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A New Biased Estimator

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    k

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    j, j = 1, . . . , p

    XRnp

    Xj, j = 1, . . . , p j x

    Tj j

    X j Xj Xj, j= 1, . . . , p

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    A Rnn A

    0

    A> 0

    i

    j

    A A{i,j} A{j} j A {0}

    0 Rp1

    j, j= 1, . . . , p

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    yi= 0+1xi,1+. . .+pxi,p+i, i= 1, . . . , n, n N,

    0, 1, . . . , p

    R

    yi

    xi,j, j= 1, . . . p p

    i E(i) = 0

    y= X + ,

    y, Rn1

    X :=

    1n X1 . . . X p

    Rn(p+1)

    1n := [1]1in X

    Xj := [xi,j]1in, j= 1, . . . , p

    X

    X

    XTX

    p+ 1

    n p + 1

    i

    2In N(0, 2In)

    2

    XTX

    RSS() :=n

    i=1

    yi xTi

    2= (y X)T (y X)=yTy + TXTX 2TXTy

    xTi , i= 1, . . . , n i X

    RSS()

    = 2XTX

    2XTy.

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    XT

    X = XT

    y

    :=

    XTX1

    XTy,

    XTX

    E() =

    () =2

    XTX

    1

    var(j) var(j), j= 0, 1, . . . , p

    E

    RSS()

    = (n p 1)2,

    RSS() =

    ni=1(yi xTi )2

    2

    2 = RSS()

    n p 1.

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    2

    := y X

    E() = 0

    () =2

    In X(XTX)1XT

    .

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    b R(p+1)1

    y

    b= C y + d.

    C R(p+1)n d R(p+1)1

    C=

    XTX1

    XT

    d= 0.

    b

    d= 0

    b

    Bias(b) = E(b) = CE(y) + d = C X + d

    (b) =C(y)CT =2CCT.

    RSS

    b

    L(b) = (b )T W(b ) ,

    W (p+ 1)(p+ 1)

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    W (p + 1) (p + 1)

    b

    R(b) = E

    (b )TW(b ) .

    W = I(p+1)

    b R(p+1)1

    MSE(b) := E

    (b )T(b )= E

    (b E(b) + E(b) )T(b E(b) + E(b) )

    = E

    (b E(b))T(b E(b)) + (E(b) )T(E(b) )= tr((b)) + Bias(b)TBias(b),

    tr

    v v2 =

    vTv MSE(b)

    b

    b

    WMSE(b)

    w R(p+1)1 MSE

    wTb

    = E

    (wTb wT)T(wTb wT)

    = E

    (b )TwwT(b ) .

    wTb

    WMSE(b)

    W =wwT

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    (p+ 1) (p+ 1)

    MtxMSE(b) := E (b )(b )T .

    MtxMSE(b) = E

    (b E(b) + E(b) )(b E(b) + E(b) )T= E

    (b E(b))(b E(b))T + (E(b) )(E(b) )T

    = (b) + Bias(b)Bias(b)T.

    tr(MtxMSE(b)) = MSE(b) = E (b )T(b )

    w R(p+1)1 wT(MtxMSE(b))w= tr

    wTE

    (b )(b )Tw

    = E

    tr

    wT(b )(b )Tw= E

    tr

    (b )TwwT(b ) .

    wT(MtxMSE(b))w 0

    W =wwT

    MSE

    wTb 0

    b1 b2

    = MtxMSE(b2) MtxMSE(b1).

    W

    WMSE(b2) WMSE(b1) 0

    W R(p+1)(p+1)

    >

    b1 b2

    := MSE(b2) MSE(b1) 0,

    b1

    b2 0

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    bi= Ciy, i= 1, 2

    = (b2) (b1) + Bias(b2)BiasT(b2) Bias(b1)BiasT(b1)=2S Bias(b1)BiasT(b1) + Bias(b2)BiasT(b2),

    S= C2C

    T2 C1CT1

    2S Bias(b1)BiasT(b1)

    Bias(b2)BiasT(b2)

    A

    (p + 1) (p + 1)

    a

    (p + 1)1

    d

    dAaaT

    aTA1a d

    dA aaT

    Bias(bi) = (CiX Ip+1), i= 1, 2.

    bi= Ciy, i= 1, 2

    S

    T(C1X Ip+1)TS1(C1X Ip+1)< 2.

    = MtxMSE(b2) MtxMSE(b1)> 0,

    S= C2CT2 C1CT1

    opt= A0y

    A0= T

    XTXTXT +2In1 ,

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    2

    ()

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    yi= 0+1xi,1+. . .+pxi,p+i, i= 1, . . . , n, n p+ 1.

    1

    n

    ni=1

    yi= 0+11

    n

    ni=1

    xi,1+. . .+p1

    n

    ni=1

    xi,p+1

    n

    ni=1

    i,

    y = 0+1 X1+. . .+p Xp+ .

    yci =1xci,1+. . .+px

    ci,p+

    ci , i= 1, . . . , n ,

    yc =Xc{0}+ c,

    T{0}:=

    1, . . . , p

    ,

    xci,j :=xi,j Xj,yci :=yi y,ci :=i , i= 1, . . . , n , j = 1, . . . , p .

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    P :=In 1n 1n1Tn Rnn,

    In n n 1n n 1

    P

    yc =P y,

    c =P ,

    Xc =P X{1},

    X{1}:=

    x1,1 . . . x1,p

    xn,1 . . . xn,p

    Rnp.

    P

    P

    P2 =P

    PT =P

    P2 =PTP = (In 1n

    1n1Tn )

    T(In 1n

    1n1Tn )

    =In

    1

    n1n1

    Tn

    1

    n1n1

    Tn +

    1

    n21n1

    Tn 1n1

    Tn

    =In 2n

    1n1Tn +

    1

    n1n1

    Tn

    =In 1n

    1n1Tn =P.

    P y= y

    y

    y

    =yc

    c =P , Xc =P X{1}

    P y= P X{1}{0}+ P .

    RSS({0}) :=

    P y P X{1}{0}T

    P y P X{1}{0}

    = y X{1}{0}T Py X{1}{0}

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    c:=

    c1, . . . ,

    cp

    c

    =

    (P X{1})TP X{1}1

    (P X{1})TP y

    =

    (P X{1})TP X{1}1

    (P X{1})T(P X{1}{0}+ P )

    ={0}+

    (P X{1})TP X{1}1

    (P X{1})TP

    ={0}+

    XT{1}P X{1}1

    XT{1}P ,

    {0}=

    1, . . . , p

    T

    E(c) ={0}+X{1}TP X{1}1 X{1}TPE() ={0}

    (c) =

    X{1}TP X{1}

    1X{1}TP()

    X{1}TP X{1}

    1X{1}TP

    T=2

    X{1}TP X{1}

    1=2

    XcTXc

    1.

    0

    c0:= y

    pi=1

    ci Xi= y

    1

    n 1Tn X{1}

    c

    .

    y= X + ,

    X=

    1n X{1}

    = 0

    {0}

    .

    =

    0

    {0}

    =

    XTX1

    XTy

    =

    1Tn 1n 1

    Tn X{1}

    X{1}T1n X{1}TX{1}

    1 1Tn y

    X{1}Ty

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    = n 1Tn X{1}

    X{1}T

    1n X{1}T

    X{1}1

    1Tn y

    X{1}T

    y .

    =

    1n+

    1n2

    1Tn X{1}Q1X{1}T1n 1n 1Tn X{1}Q1

    1n Q1X{1}T1n Q1

    1Tn y

    X{1}Ty

    =

    1n 1

    Tn y +

    1n2

    1Tn X{1}Q1X{1}T1n1Tn y 1n 1Tn X{1}Q1X{1}Ty

    1n Q1X{1}T1n1Tn y + Q1X{1}Ty

    ,

    Q= X{1}TX{1} 1n(1Tn X{1})T(1Tn X{1})=X{1}TP X{1}=

    P X{1}

    TP X{1}.

    {0}= 1

    nQ1X{1}T1n1Tn y + Q

    1X{1}Ty

    = 1n

    X{1}TP X{1}

    1X{1}T1n1Tn y

    +

    X{1}TP X{1}

    1

    X{1}Ty

    = X{1}TP X{1}1X{1}Ty 1n 1Tn X{1}T 1Tn y=

    X{1}TP X{1}1

    XT{1}P y

    =

    (P X{1})TP X{1}1

    (P X{1})TP y

    {0}= c.

    0=

    1

    n1

    T

    n y +

    1

    n21

    T

    n X{1}Q1

    X{1}T

    1n

    1T

    n y 1

    n1

    T

    n X{1}Q1

    X{1}T

    y

    = y+1

    n1

    Tn X{1}

    X{1}TP X{1}

    1X{1}T1ny

    1n

    1Tn X{1}

    X{1}TP X{1}

    1X{1}Ty

    = y 1n

    1Tn X{1}

    XT{1}P X{1}

    1XT{1} (y 1ny)

    = y 1n

    1Tn X{1}

    X{1}TP X{1}

    1X{1}TP y

    = y 1n

    1Tn X{1}{0}

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    0= c0.

    XTX

    y := yc

    zi,j =xi,j Xj

    Sjj, i= 1, . . . , n , j = 1, . . . , p

    Sjj =n

    i=1

    (xi,j Xj)2.

    yi =1zi,1+2zi,2+ +pzi,p+i , i= 1, . . . , n ,

    y = Z + ,

    y = P y,

    Z=:

    Z1 . . . Z p

    = P X{1}D1,

    = D{0},

    = P

    D=

    S11

    Spp

    .

    Zj := [zi,j]1in, j = 1, . . . , p Z

    =

    ZTZ

    1

    ZTy

    = D1XT{1}P X{1}D11 D1XT{1}P y

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    =D XT{1}P X{1}

    1XT{1}P y= D{0}

    j = j

    1

    Sjj

    12

    , j= 1, . . . , p

    0 = y p

    j=1

    j Xj .

    E() =DE({0}) =D{0}.

    () =

    ZTZ1

    ZT(y)Z

    ZTZ1

    =

    ZTZ1

    ZTP(y)PTZ

    ZTZ1

    =2

    ZTZ1

    ZTP Z

    ZTZ1

    =2 ZTZ1 2

    n ZTZ1

    ZT1n1Tn ZZTZ1

    =2

    ZTZ1

    ,

    Z ZT1n= 0 Rp1

    (XTX)1

    E() = 0

    () =P()PT =2P,

    RSS() = (y Z)T (y Z)

    =

    P y P X{1}{0}T

    P y P X{1}{0}

    = P y P X{1}{0} P 0TP y P X{1}{0} P 0

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    T0 :=

    0, . . . , 0 R1n

    P 0= 0

    RSS() =

    y XT

    P

    y X

    = TP.

    E() = 0,

    () =2

    In X(XTX)1XT

    E (RSS()) = E

    TP

    = ET(In 1n 1n1Tn )= E

    T

    1n

    E

    T1n1Tn

    = (n p 1)2 1n

    tr(1n1Tn ())

    = (n p 1)2 2

    ntr

    1n1Tn (In X(XTX)1XT)

    = (n p 2)2 +

    2

    n 1

    Tn X(X

    TX)1XT1n.

    E (RSS()) = ERSS() .

    2

    2 = RSS()

    n p 2 + 1n 1Tn X(XTX)1XT1n.

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    Z1 Z2

    1,2

    y,i

    y Zi, i= 1, 2 =

    ZTZ

    1ZTy

    ZTZ

    1=

    1 1,2

    1,2 1

    |ZTZ| ,

    |ZTZ| = 1 21,2 21,2 1 |ZTZ| 0 var(i) , i= 1, 2 cov(i, j)

    1,2

    1

    () =2

    ZTZ1

    .

    Z1 Z2

    =

    y,1 1,2y,2y,2 1,2y,1

    |ZTZ

    |

    .

    1,2 = 1 |ZTZ| = 0

    1+ 2= (y,1(1 1,2) +y,2(1 1,2))|ZTZ|1 =(y,1+y,2)

    (1 +1,2)

    1,2= 1

    1 2= (y,2 y,1)(1 1,2)

    (1+ 2)

    (1

    2)

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    p

    () =2

    ZTZ1

    .

    ZTZ = VVT

    pj=1

    var(j) =2tr(V1VT) =2tr(VTV

    =Ip

    1) =2

    pj=1

    1

    j,

    j, j = 1, . . . , p Z

    TZ

    Zj, j = 1, . . . , p

    var(j ) =

    2p

    k=1

    v2j,k

    k ,

    vj,k (j, k) V =: [vj,k]1j,kp p

    p

    vj,k

    p

    (ZTZ)1

    rj,j =

    1

    1 R2j , j = 1, . . . , p ,

    R2j

    Zj (p 1)

    R2j , j = 1, . . . , p

    rj,j j

    var(j) = 2

    1 R2j, j = 1, . . . , p ,

    R2j

    j

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    Z y y yp y = Z = Z

    ZTZ

    1ZTy yp= Z

    ZTZ

    1ZTyp Z+yp2

    2 cond(ZTZ)

    y yp2y2

    ,

    Z+ :=

    ZTZ1

    ZT 2 y

    cond(ZTZ) ZTZ

    cond(ZTZ) 1

    (Z+ E)+yp22

    cond(ZTZ) E12

    + cond(ZTZ)2 E22y y2

    y2+ cond(ZTZ)3 E222,

    E

    E= E1+ E2 E1

    E

    Z

    E2

    Z

    cond(ZTZ)

    y

    Z

    2 0

    L2 := [ ]T [ ] .

    E(L2) = MSE() =2tr(ZTZ)1 =2p

    j=1

    1

    j

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    E(T) = E yTZ(ZTZ)2ZTy= E

    (Z+ )TZ(ZTZ)2ZT(Z+ )

    =T+ E

    TZ(ZTZ)2ZT

    ,

    E() = 0

    E(T) =T+ tr

    Z(ZTZ)2ZT()

    =T+2tr

    (ZTZ)1

    ,

    ZT

    1n =

    0

    T

    T

    j, j = 1, . . . , p

    pT

    p Rp1 ZTZ p

    ZTZ

    pT pTp= 1

    pT = V1 V1

    ZTZ

    pT pT = Vp

    t

    R2

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    j

    i,j, i , j= 1, . . . , p , i =j X

    Xi Xj, i ,j= 1, . . . , p, i =j

    i,j

    i,j i,j

    rj,j, j = 1, . . . , p

    VIFj :=rj,j = 1

    1 R2j=

    var(j)2

    , j = 1, . . . , p .

    ZTZ rj,j = 1

    VIFj, j = 1, . . . , p

    j

    10

    ZTZ

    1, . . . , p ZTZ

    Z

    cond(ZTZ) =max(Z

    TZ)

    min(ZTZ)

    .

    ZTZ

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    cond(Z

    T

    Z)

    ZTZ

    condj(ZTZ) =

    max(ZTZ)

    j(ZTZ)

    , j= 1, . . . , p .

    ZTZ

    Z

    n p

    Z

    Z=UVT,

    U Rnp, V Rpp

    Rpp

    k, k= 1, . . . , p

    Z

    Z

    condk(Z) =max(Z)

    k(Z) , k= 1, . . . , p .

    Z

    () =2V2VT

    j

    var(j) =2

    pk=1

    v2j,k2k

    =2VIFj, j = 1, . . . , p .

    var(j)

    p

    k

    2k

    var(1) var(2) var(p)

    1 1,1 1,2 1,p2 2,1 2,2 2,p

    p p,1 p,2 p,p

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    k

    j,k :=v2j,k2k

    VIFj =

    p

    k=1j,k, j, k= 1, . . . , p .

    j,k := j,kVIFj

    .

    j,k

    j

    k

    XTX

    ZTZ

    ZTZ

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    y

    X1

    X2

    X3

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    y= 0+1X1+2X2+3X3+

    y= X +

    N(0, 2I17)

    T

    :=

    0, 1, 2, 3

    T :=

    0, 1, 2, 3

    R2 p t

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    y

    X1

    1

    X

    10

    X

    X

    XTX

    XTX

    X

    max

    XTX j, j = 2, 3

    X

    cond(X) = maxmin = 3.936520.00003568 = 332.15196,

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    95

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    r

    (ZTZ+kIp)r = ZTy,

    r = (ZTZ+kIp)1ZTy,

    k >0

    k= 0

    r =

    ZTZ+kIp1

    ZTy

    =

    ZTZ+kIp1

    ZTZ

    ZTZ1

    ZTy

    =

    ZTZ+kIp

    1

    ZTZ

    = Ip+k(ZTZ)11 =Kr,

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    Kr :=

    Ip+k(ZTZ)1

    1

    =Ip k ZTZ+kIp

    1

    E(r) = E(Kr

    ) = Kr

    r

    Bias(r) = E(r) = (Kr Ip) = k ZTZ+kIp1

    BiasT(r)Bias(r) =k2T

    ZTZ+kIp

    2.

    r

    (r) = (ZTZ+kIp)

    1ZT(y)Z(ZTZ+kIp)1

    = (ZTZ+kIp)1ZT()Z(ZTZ+kIp)1

    = (ZTZ+kIp)1ZTP()PTZ(ZTZ+kIp)1

    =2(ZTZ+kIp)1ZT

    In 1

    n1n1

    Tn

    Z(ZTZ+kIp)

    1

    =2(ZTZ+kIp)1ZTZ(ZTZ+kIp)1

    =2Kr(ZTZ+kIp)

    1 =:2KrZr,

    ZT1n Z j, j =

    1, . . . , p ZTZ

    ZTZ=VVT

    =

    1

    p

    VTV =Ip.

    Vj V j, j = 1, . . . , p

    ZTZ

    (ZTZ)1 =V1VT.

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    (ZTZ)1 ZTZ 1j

    Vj, j= 1, . . . , p

    j Z

    TZ

    Vj , j= 1, . . . , p

    Zr = (Z

    TZ+kIp)1

    j =

    1j+k

    Vj

    Kr =

    k(ZTZ)1 + Ip

    1

    j = jj+k

    Vj

    j = 1, . . . , p

    j Z

    TZ

    Vj

    ZTZVj =jVj, j= 1, . . . , p .

    ZTZ+kIp

    Vj = (j+k) Vj , j= 1, . . . , p .

    (ZTZ+ kIp) j+ k Vj

    (ZTZ+ kIp) k >0

    Kr

    j := 1j+k

    Vj

    (ZTZ)1

    1j

    Vj, j = 1, . . . , p

    (ZTZ)1Vj = 1

    jVj

    k(ZTZ)1Vj = kj

    Vj

    k(ZTZ)1 + IpVj = kj

    + 1

    Vj, j = 1, . . . , p .

    Kr j = kj + 11 = jj+k

    Vj

    pj=1

    var(rj ) =2tr

    V

    1

    p

    VTV

    1

    p

    VT

    =2tr1

    p 1

    p = 2

    p

    j=1j

    (j+ k)2

    .

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    r

    k

    r

    MSE(r) =

    pj=1

    var(rj ) + biasT(r)bias(r)

    =2p

    j=1

    j(j+k)2

    +k2T(ZTZ+kI)2.

    r

    k

    k

    r

    k >0

    MSE(r)< MSE().

    r

    RSS(r) = (y Zr)T (y Zr)

    = ((y Z) + (Z Zr))T ((y Z) + (Z Zr))= (y Z)T(y Z) + 2(y Z)T (Z Zr)

    + ( r)TZTZ( r)= (y Z)T(y Z) + ( r)TZTZ( r)= RSS() + ( r)TZTZ( r),

    Z= ZZTZ1 ZTy 2(y Z)T (Z Zr) = 2yT

    In Z

    ZTZ

    1ZT

    Z( r) = 0.

    X

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    g

    RSS(g) = (y Zg)T(y Zg)= (y Z)T(y Z) + (g )TZTZ(g )= RSS() +(g).

    RSS(g)

    RSS(g) RSS()

    (g ) g0

    RSS(g0

    ) = RSS() +0

    0

    > 0

    ZTZ

    ZTZ

    min gTg

    (g )TZTZ(g ) =0.

    F :=gTg +1

    k

    (g )TZTZ(g ) 0

    ,

    1k

    F

    g = 2g +

    1

    k

    2ZTZg 2ZTZ= 0.

    r :=

    Ip+

    1

    kZTZ

    1 1k

    ZTZ

    =

    ZTZ+kIp1

    ZTy,

    k

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    r

    k

    k

    k

    k

    r k k (0, 1]

    k

    k

    r

    k

    r

    k

    k

    k

    k

    k= p2

    T,

    2 2

    k= p2

    T ZTZ= Ip

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    K

    N(0, 2In) E (RSS()) =2(n p).

    2 = RSS(

    )np

    2

    k

    k

    k0

    ki= p2p

    j=1(j(ki1))2, i 1,

    ki k

    Q

    Q:= T 2p

    j=1

    1j

    ,

    j Z

    TZ

    k

    r(k)Tr(k) =Q,

    Q> 0

    k= 0

    k=

    k

    r k

    k

    E(T) =T+2tr

    (ZTZ)1

    .

    k

    T

    E(r(k)Tr(k)) = E(

    T) 2p

    j=1

    1

    j

    =T.

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    Q

    k= 0

    k=

    k

    r(k)Tr(k) = abs(Q)

    abs(Q)

    Q

    y= X + ,

    N(0, 2

    In)

    2 =RSS()

    n p

    2

    k

    k

    1.0

    10

    kI

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    k

    k

    k

    k

    k

    ZTZ

    ZTZ

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    ZTZ

    kIp X

    TX R(p+1)(p+1) X

    bTb

    min bTHb,

    b

    (b )TXTX(b ) =0.

    H

    R(p+1)(p+1)

    Fg := bTHb +

    1

    k

    (b )TXTX(b ) 0

    .

    XTX

    g =

    XTX+kH1

    XTy.

    H=Ip+1

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    H = 1k G G R(p+1)(p+1)

    g =

    XTX+ G1

    XTy.

    XTX = VVT

    V

    H = 1k V KV

    T

    K

    g = XTX+ V KVT1 XTy.

    H=XTX

    g =

    (1 +k)XTX1

    XTy

    = 1

    1 +k= , [0, 1].

    s := 1 c2

    T

    Z

    T

    Z ,

    c > 0

    c R

    2

    k

    (g) =

    2 XTX+kH1 XTX XTX+kH1

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    Bias(g) = E(g) = XTX+kH1 XTX =

    XTX+kH1

    XTX Ip.

    XTX+kH

    1 XTX

    Ip= XTX+kH1 kH

    MtxMSE(g) =

    XTX+kH1

    k2HTH+2XTX

    XTX+kH1

    .

    g

    := MtxMSE() MtxMSE(g)

    T2

    kH1 + (XTX)11 2,

    H

    =2

    XTX1 XTX+kH1 k2HTH

    +2XTX

    XTX+kH

    1 0.

    = UT

    U

    U

    p H

    XTX+kH

    pT

    XTX+kH

    XTX+kH

    p

    =pT

    XTX+kH

    UTU

    XTX+kH

    p

    =pT

    U

    XTX+kHT

    U

    XTX+kH

    p 0, p

    R(p+1)1

    (XTX+ kH)

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    2 XTX+kH XTX1 XTX+kH k2HTH 2XTX 0.

    2

    XTX+kH

    XTX1

    XTX+kH

    =2

    XTX+ 2kH+k2H

    XTX1

    H

    2 2kH+k2HX

    TX1

    H k2HTH 0.

    1k H

    1

    2

    2

    kH1 +

    XTX

    1 T 0.

    pTg, p R(p+1)1

    T

    2

    kIp+

    XTX

    1 2,

    T2G1 + XTX1 2

    G

    T

    2K1 +

    XTX1

    2,

    T

    XTX

    k+ 2k

    2.

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    bg =

    XTX+ C+

    XTy,

    XTX+ C

    +

    XTX+ C+

    C

    XTX

    C

    Z

    Z= UVT.

    =

    ZTZ

    1

    ZTy= V1VTV12 UTy

    =V

    12

    UT

    y,

    ZTZ

    r =V 1

    2 UTy,

    1, . . . , p R

    W

    j = jj+k

    , j = 1, . . . , p

    B

    B

    W

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    k

    N(0, 2I17)

    2

    2 = RSS()

    n

    p

    1

    = 11.369

    17

    3

    1

    = 0.87453.

    r

    k

    r =

    ZTZ+kI31

    ZTy.

    r{0}

    T :=

    r1, r2,

    r3

    {0}T =

    1, 2, 3

    k

    r{0}= D

    1r = D1 ZTZ+kI31 ZTy,

    D

    r0 = y

    3

    j=1 r

    jXj .

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    k

    k

    k

    0.05

    k

    k

    k

    10

    k 0.05

    k

    y = Z +

    T = 19.106, 24.356, 6.4207 .

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    k

    k

    k = 42ZT

    2Z=RSS()

    n p =11.368

    14 = 0.8120,

    2

    RSS()

    k= 0.00325.

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    k

    r

    (k) =3.3497, 0.3787, 1.5042, 7.8142 104

    T.

    k

    r(k)Tr(k) T 2tr

    (ZTZ)1

    .

    2Z

    2

    QZ := T

    2Ztr (ZTZ)1= 138.0

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    kZ= 0.0033.

    r

    (k) =3.3781, 0.3642, 1.4962, 7.80 104

    T.

    k

    2

    2 = RSS()1731 = 0.87453

    k

    MSEk(r) = 2

    pj=1

    j(j+ k)2

    +k2T(ZTZ+kI)2.

    r

    k

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    kmin= 0.0012

    kmin

    MSE(kmin) = 517.06.

    kmin= 0.0012

    r

    (k) =0.7410, 1.6031, 2.0893, 0.0012

    T.

    k

    k

    k

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    j

    Zj, j = 1, . . . , p

    Z

    n p

    n > p

    Zj, j = 1, . . . , p

    min

    ni=1

    (yi zTi T)2,

    zTi i Z

    T =

    1, . . . , p

    = 0

    R

    min (y (Z+

    ))

    T

    (y (Z+

    )) ,

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    :=

    1 . . . p

    1 . . . p

    Rnp, n > p.

    (Z+)T (Z+) = (Z+)T y.

    y

    ni=1y

    i = 0

    Ty = 1

    ni=1y

    i

    pn

    i=1yi

    = 0 Rp1.

    Z

    TZ=ZT= 0.

    M= [mu,v]1u,vp :=

    Z+T

    Z+

    = ZTZ+2T.

    M ZTZ

    T

    pTMp= pT

    ZTZ

    p +2pT

    T

    p> 0

    p Rp1

    =

    (Z+)T (Z+)1

    (Z+)T y

    =

    ZTZ+2T1

    ZTy.

    2T

    M

    M{u,v} (p 1) (p 1)

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    M u v

    M{u,v}=

    m1,1 . . . m1,v1 m1,v+1 . . . m1,p

    mu1,1 . . . mu1,v1 mu1,v+1 . . . mu1,pmu+1,1 . . . mu+1,v1 mu+1,v+1 . . . mu+1,p

    mp,1 . . . mp,v1 mp,v+1 . . . mp,p

    , u , v= 1, . . . , p .

    M

    M1 =M

    |M

    |,

    M:= [mu,v]1u,vp Rpp M mu,v := (1)u+v

    M{v,u} .

    M1x :=(X+)T(X+)

    1 X Rnp

    X

    n p

    n p

    n p

    n p j , j = 1, . . . , p Mx = (X+)

    T(X+)

    |Mx| =2TAx + 2bxT + |XTX|,

    T :=

    1, . . . , p

    ,

    bxT :=

    |XTX[1]|, . . . , |XTX[p]|

    Ax:=

    |X[1]TX[1]| . . . |X[1]TX[p]|

    |X[p]TX[1]| . . . |X[p]TX[p]|

    ,

    X[j], j = 1, . . . , p n p X j

    X

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    |Mx| =

    1j1...jpn

    (X+)T

    1 . . . p

    j1 . . . jp

    2

    =

    1j1...jpn

    XT

    1 . . . p

    j1 . . . jp

    +T

    1 . . . p

    j1 . . . jp

    2

    .

    p p

    XT

    1 . . . p

    j1 . . . jp

    T

    1 . . . p

    j1 . . . jp

    s=

    n

    p

    {j1, . . . , jp} 1j1 . . .jp n p {1, . . . , n} {j1,k, . . . , jp,k}, k= 1, . . . , s

    XT k :=XT

    1 . . . p

    j1,k . . . jp,k

    T k := T

    1 . . . p

    j1,k . . . jp,k

    k

    {j1,k, . . . , jp,k

    }

    {1, . . . , n

    }

    XT k +T k , k = 1, . . . , s

    {i1, . . . , ir} {1, . . . , n} |C{i1,...,ir}p |k p p i1, . . . , ir i1, . . . , ir

    T k XT k

    k = 1, . . . , s

    r 2 C{i1,...,ir}p

    T k |C{i1,...,ir}p |k = 0, r 2 r= 1 ir =r

    C{r}p k =r|X[r]T

    k

    |,

    X[r]

    T k

    XT k

    r

    XT k

    |C{}p|k =|XT k |

    XT k +T k= {i1,...,ir}

    C{i1,...,ir}p k

    = |XT k | +p

    r=1

    C{r}p k

    = |XT k | +1|X[1]T k | +. . .+p|X[p]T k |, X[j]

    T k , j = 1, . . . , p XT k

    j

    XT

    k

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    |Mx| =s

    k=1

    |XT k | +

    pr=1

    C{r}p k

    2

    =s

    k=1

    |XT k |2 + 2|XT k |

    pr=1

    r|X[r]T k |

    +2p

    t=1

    pr=1

    rt|X[r]T k ||X[t]T k |

    =s

    k=1|XT k |2 + 2

    p

    r=1r

    s

    k=1|XT k ||X[r]T k |

    +2p

    t=1

    pr=1

    rt

    sk=1

    |X[r]T k ||X[t]T k |.

    |XTX| =s

    k=1

    |XT k |2,

    |XTX[r]| =s

    k=1

    |XT k ||X[r]T k |,

    |X[r]TX[t]| =s

    k=1

    |X[r]T k ||X[t]T k |

    |Mx| =2p

    t=1

    pr=1

    rt|X[r]TX[t]| + 2p

    r=1

    r|XTX[r]| + |XTX|.

    |Mx| =2TAx + 2bxT + |XTX|.

    ARpn B Rnp np

    |AB

    |=

    1j1...jpn A1 . . . p

    j1 . . . jp B j1 . . . jp

    1 . . . p

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    |Mx

    |=

    3

    k=1 |XT

    k

    +T

    k

    |2

    =

    XT

    1 2

    1 2

    +T

    1 2

    1 2

    2

    +

    XT

    1 2

    1 3

    +T

    1 2

    1 3

    2

    +

    XT

    1 2

    2 3

    +T

    1 2

    2 3

    2

    =

    1 21 5

    +

    1 1

    0 0

    2

    +

    1 21 3

    +

    1 1

    0 0

    2

    + 2 25 3 + 1 10 0 2

    XT k +T k= {i1,...,ir}

    C{i1,...,ir}p k

    ,

    {1, 2} {}

    {1}

    ,{

    2}{1, 2}.

    C{i1,...,ir}p 2 2 i1, . . . , ir i1, . . . , ir

    T k

    XT k

    1 21 5

    +

    1 1

    0 0

    =1 21 5

    +

    1 1

    1 5

    + 1 20 0 +

    1 1

    0 0

    1 21 5

    +

    1 1

    0 0

    =1 21 5

    +1

    1 1

    1 5

    1 21 3

    +

    1 1

    0 0

    =

    1 21 3

    +1

    1 1

    1 3

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    2 2

    5 3 + 1 1

    0 0 = 2 2

    5 3+1 1 1

    5 3

    |Mx| =1 21 5

    +1

    1 1

    1 5

    2

    +

    1 21 3

    +1

    1 1

    1 3

    2

    +

    2 2

    5 3

    +1

    1 1

    5 3

    2

    .

    X[1]

    XTX[1] =1 2 2

    1 5 3

    1 11 51 3

    X[1]TX[1] =

    1 1 1

    1 5 3

    1 11 51 3

    .

    |XTX| = 1 21 52

    + 1 21 32

    + 2 25 32

    ,

    |XTX[1]| =1 21 5

    1 1

    1 5

    +1 21 3

    1 1

    1 3

    +

    2 2

    5 3

    1 1

    5 3

    ,|X[1]TX[1]| =

    1 1

    1 5

    2

    +

    1 1

    1 3

    2

    +

    1 1

    5 3

    2

    |Mx

    |=221

    |X[1]

    TX[1]|

    + 21|XTX[1]

    |+

    |XTX

    |.

    Mx i= 0, 1 i q

    1 qp

    i= 0, i > q

    TAx=

    qs=1

    qr=1

    rs|X[r]TX[s]| =Tq Aqxq,

    bTx =

    q

    r=1 r|XTX[r]

    |=bqx

    Tq

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    Tq :=1, . . . , q ,

    bqxT :=

    |XTX[1]|, . . . , |XTX[q]|

    ,

    Aqx:=

    |X[1]TX[1]| . . . |X[1]TX[q]|

    |X[q]TX[1]| . . . |X[q]TX[q]|

    .

    |Mx|

    2Tq Aqxq+ 2b

    qx

    T + |XTX| = 0.

    1, 2

    1/2=2bqxTq

    4

    (bqxTq)

    2 Tq Aqxq|XTX|

    2Tq Aqxq

    D:= 4

    (bqxTq)

    2 Tq Aqxq|XTX|

    .

    |Mx|

    Aqx

    Ru, u= 1, . . . , m n p n p

    R=

    |RT1 R1| |RT1 R2| . . . |RT1 Rm||RT2 R1| |RT2 R2| . . . |RT2 Rm|

    |RTmR1| |RTmR2| . . . |RTmRm|

    R= RT

    R,

    RT

    :=

    RT11 . . . RT1s

    RTm 1 . . . RTm s Rms

    s=

    n

    p R

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    |RTu Rv| =|RTv Ru|, u , v = 1, . . . , m

    |RTu Ru| =

    1j1...jpn

    RTu

    1 . . . p

    j1 . . . jp

    2

    =s

    k=1

    RTuk2 , u= 1, . . . , m

    |RTu Rv| =

    1j1...jpn

    RTu

    1 . . . p

    j1 . . . jp

    RTv

    1 . . . p

    j1 . . . jp

    =

    s

    k=1 RTuk

    RTvk

    u, v= 1, . . . , m , u =v.

    s =

    n

    p

    {j1,k, . . . , jp,k}, k = 1, . . . , s {1, . . . , n}

    R= RT

    R R

    R

    Aq

    x= A

    TA

    AT

    =

    X[1]T 1 . . . X[1]T s

    X[q]T 1 . . . X[q]T s Rqs,

    Aqx

    Tq A

    qxq 0 Tq Aqxq > 0 |Mx|

    Aqx bqx |XTX| = 0

    B:= Aqx bqxb

    qx

    T

    |XTX|

    B 0

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    G:=

    Aqx b

    qx

    bqxT |XTX|

    =

    |X[1]TX[1]| . . . |X[1]TX[q]|

    |X[q]TX[1]| . . . |X[q]TX[q]|

    |XTX[1]|

    |XTX[q]|

    |XTX[1]| . . . |XTX[q]| |XTX|

    ,

    R(q+1)(q+1).

    |XTX

    |=

    1j1...jpn XT 1 . . . pj1 . . . jp

    2

    =s

    k=1

    XT k2

    =XTX

    ,

    XT :=

    XT 1 , . . . , XT s R1s.

    AT

    X

    =

    X[1]T 1 . . . X[1]T s

    X[q]T 1 . . . X[q]

    T s

    XT 1

    XT s

    =

    |X[1]TX|

    |X[q]TX|

    =|XTX[1]|

    |XTX[q]|

    =bqx,

    sk=1

    X[i]T k XT k= |X[i]TX|, i= 1, . . . , q ,

    G= AT

    A AT

    X

    XTA X

    TX= A

    T

    XT A X R(q+1)(q+1)

    G

    Aqx

    bqxbqx

    T

    |XTX|

    0.

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    0 Tq

    Aqx bqxbqxT|XTX|

    q =Tq A

    qxq (Tq bqx)(bqxTq)|XTX|

    =Tq Aqxq

    (Tq bqx)

    2

    |XTX| bqxT2 TAqx|XTX| 0,

    D

    |Mx|

    |Mx| = 0 |Mx|

    s=

    n

    p

    =

    n!

    (n p)!p! =n(n 1) (n 2) . . . (p+ 1)

    p (p 1) . . . 2 1 n, p < n

    G

    A X

    Rs(q+1), qp

    rank

    A X

    = q+ 1

    G

    q= p = n

    s = 1

    rank

    A X

    = 1

    X

    X

    = 0

    rank A X< q+ 1

    j

    X

    c R

    X

    j

    A

    rank

    A X

    < q+ 1

    G

    G |Mx|

    |Mx| |Mx| >0

    Mx

    |Mx| 0 Mx (X+ )

    p

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    X np np

    n p

    j, j = 1, . . . , p

    Mx=

    X+T

    X+

    M1x =Mx

    |Mx| = 2 M

    quadx + M

    linx + M

    constx

    2TAx + 2bTx + |XTX|

    ,

    Mquadx :=

    mquadx u,v

    1u,vp

    =

    (1)u+v{u}TA

    (uv)x {v}

    1u,vp

    ,

    M

    lin

    x := mlinx u,v1u,vp = (1)u+v b(uv)x T{v}+ b(vu)x T{u}1u,vp ,

    Mconstx :=

    mconstx u,v

    1u,vp=

    (1)u+v X{u}TX{v}

    1u,vp

    {u}:=

    r

    1rpr=u

    R(p1)1,

    b(uv)x :=

    X{u}TX{v}[r]

    1rpr=v R(p1)1,

    A(uv)x :=

    X{u}[r]TX{v}[s] 1r,spu=r;v=s

    R(p1)(p1).

    X{u} Rn(p1) u X X{u}[r]

    X

    r

    X

    u

    Mx =:

    mxu,v

    1u,vp Mx

    X{u}, {u} X{v}, {v} n (p 1)

    X

    u

    v

    mxv,u = mxu,v = (1)u+v

    X{u}+{u}TX{v}+{v}= (1)u+v

    sk=1

    X{u}T k +{u}T k X{v}T k +{v}T k ,

    s :=

    n

    p 1

    (p 1)

    {1, . . . , n}

    k

    k= 1, . . . , s

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    X{u}T k +{u}T k

    :=

    X{u}T 1 . . . p 1j1,k . . . jp1,k +{u}T 1 . . . p 1j1,k . . . jp1,k .

    X{u}T k +{u}T k= |X{u}T k | + pr=1

    r=u

    r|X{u}[r]T k |

    X{v}T

    k

    +

    {v

    }

    T

    k

    = |X{v}T

    k

    |+

    p

    s=1s=v

    s

    |X

    {v

    }[s]

    T

    k

    |,

    X{u}[r], r = 1, . . . , p, r=u X{u}

    r X X{u}

    mxu,v = (1)u+vs

    k=1

    |X{u}T k ||X{v}T k |

    +

    p

    s=1s=vs|X{u}T k ||X{v}[s]T k | +

    p

    r=1r=ur|X{v}T k ||X{u}[r]T k |

    +2ps=1

    s=v

    pr=1

    r=u

    rs|X{u}[r]T k ||X{v}[s]T k |

    = (1)u+v2 p

    s=1s=v

    pr=1r=u

    rs|X{u}[r]TX{v}[s]| +ps=1s=v

    s|X{u}TX{v}[s]|

    +

    p

    r=1r=ur|X{v}TX{u}[r]| + |X{u}TX{v}|

    =2mquadx u,v+mlinx u,v+ m

    constx u,v

    Mquadx

    Mlinx

    Mconstx p p

    Mconstx X

    TX

    = 0

    XTX

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    |Mx|

    Mx

    Z Rnp, n > p

    M =

    Z+T

    Z+

    = ZTZ+2T,

    Z

    ZTZ[v] =

    Z12 . . . Z 1TZv1 0 Z1TZv+1 . . . Z 1TZp

    ZpTZ1 . . . Z pTZv1 0 ZpTZv+1 . . . Zp2

    |ZTZ[v]| = 0, v= 1, . . . , p

    bx= 0

    Z[u]TZ[v] =

    Z12 . . . Z 1TZv1 0 Z1TZv+1 . . . Z 1TZp

    Zu1TZ1. . . Z u1TZv1 0Zu1TZv+1. . . Z u1TZp0 . . . 0 n 0 . . . 0

    Zu+1TZ1. . . Z u+1

    TZv1 0Zu+1TZv+1. . . Z u+1TZp

    ZpTZ1 . . . Z p

    TZv1 0 ZpTZv+1 . . . Zp2

    |Z[u]TZ[v]| = (1)u+vn|Z{u}TZ{v}|, p 2, u , v= 1, . . . , p .

    Z

    Ax

    n

    |ZTZ|

    Ax = n

    (1)u+v Z{u}TZ{v}

    1u,vp

    r =u

    s =v|Z{u}TZ{v}[s]| = 0

    |Z{u}[r]T

    Z{v}[s]| = (1)r+s

    n|Z{ur}T

    Z{vs}|, p 3,

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    Z{ur}, r = 1, . . . , p u r Z

    Z{1}[2]= Z{2}[1] = 1n

    p= 2

    |Z{u}[r]TZ{v}[s]| =n, u, v , r, s = 1, 2; r =u; s =v.

    b(uv)x = 0

    A(uv)x = n , p= 2

    (1)r+sn|Z{ur}TZ{vs}|1r,spu=r;v=s

    , p 3.

    (5) mu,v = (1)u+vn2 p

    r=1r=u

    ps=1s=v

    (1)r+srs|Z{ur}TZ{vs}| + |Z{u}TZ{v}|

    ,

    1 u, vp, p 3

    p= 2

    mu,v = (1)u+vn2 2

    r=1

    r=u

    2s=1

    s=v

    rs+ |Z{u}TZ{v}|

    , u, v= 1, 2.

    Z

    Z

    n p

    n > p, p 2

    np

    j, j = 1, . . . , p M =

    (Z+)T(Z+) =ZTZ+2T

    M1 =M

    |M| = n2 M

    quad+ M

    const

    n2T Mconst

    + |ZTZ|,

    Mquad

    :=

    mquadu,v

    1u,vp

    :=

    (1)u+v{u}TA

    (uv){v}

    1u,vp

    ,

    Mconst

    := mconstu,v 1u,vp:= (1)u+v Z{u}

    TZ

    {v

    }1u,vp ,

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    {u}:= r 1rpr=u

    R(p1)1,

    A(uv)

    :=

    1 , p= 2(1)r+s|Z{ur}TZ{vs}|

    1r,spu=r;v=s

    , p 3 R(p1)(p1).

    Mconst

    ZTZ

    Mconst

    =

    |ZTZ

    | ZTZ

    1

    Rpp.

    ZTZ

    ZTZ |ZTZ| >0

    Mconst

    n2T M

    const 0 |ZTZ| >0 Z

    |M| >0

    M

    Z

    ZT =

    2 1 12 2 0

    ,

    X

    T =

    1 1 1

    0 0 0

    .

    ZTZ= 6 66 8

    =

    1 0

    .

    A(11)

    = A(12)

    = A(21)

    = A(22)

    = 1,

    {1}= 0,

    {2}= 1

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    Mquad=0 0

    0 21

    ,

    Mconst

    =

    8 66 6

    M1 =

    n2

    0 0

    0 21

    +

    8 66 6

    n2218 + 6 66 8

    = 1

    24221+ 12

    3221

    0 0

    0 1

    +

    8 66 6

    .

    |M|

    M

    M1

    = (ZTZ+2T)1ZTy

    = n2 M

    quad+ M

    const

    n2T Mconst

    + |ZTZ|ZTy,

    Mquad

    =

    mquadu,v

    1u,vp

    =

    (1)u+v{u}TA

    (uv){v}

    1u,vp

    ,

    Mconst =

    mconstu,v

    1u,vp =

    (1)u+v Z{u}TZ{v}

    1u,vp.

    = 0

    0=M

    const

    |ZTZ| ZTy= .

    Z

    y=

    10

    1

    .

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    = 1

    24221+ 12

    3221

    0 0

    0 1

    +

    8 66 6

    2 1 12 2 0

    101

    = 1

    2221+ 1

    1

    0.5(221 1)

    .

    = 0

    = 1

    0.5 .

    1= 1

    0 1 2 3 4 5

    0.5

    0

    0.5

    1

    1

    2

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    =:

    1 . . .

    p

    T

    () = (ZTZ+2T)1ZT(y)Z(ZTZ+2T)1

    = (ZTZ+2T)1ZT()Z(ZTZ+2T)1

    = (ZTZ+2T)1ZTP()PTZ(ZTZ+2T)1

    =2(ZTZ+2T)1ZT

    In 1n

    1n1Tn

    Z(ZTZ+2T)1

    =2(ZTZ+2T)1ZTZ(ZTZ+2T)1,

    ZT1n Z

    () =2(ZTZ+2T)1(ZTZ+2T2T)(ZTZ+2T)1

    =2(ZTZ+2T)1 22(ZTZ+2T)1T(ZTZ+2T)1

    =2 n2 M

    quad+ M

    const

    n2T Mconst

    + |ZTZ|

    22 n2 M

    quad+ M

    const

    n2

    T

    M

    const

    + |ZT

    Z|

    T

    n2 Mquad

    + Mconst

    n2

    T

    M

    const

    + |ZT

    Z|.

    A Rp(p+1)A{r}[l]= (1)(lr+1) A{l}[r] , 1 r, l p, l =r, A{r}[l] A l

    r

    A{r}[l] A{l}[r]

    l > r

    A{r}[l] A{l}[r] r

    (r+ 1)

    (r+ 1)

    (r + 2)

    (l 1)

    A{l}[r]

    = l 2 l 1 . . .r+ 1 r+ 2r r+ 1 .

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    sign() = (1)(l1)r = (1)lr+1.

    sign()

    A{r}[l]= (1)(lr+1) A{l}[r] , 1 r < l p.

    l

    r

    l < r A{l}[r]= (1)(rl+1) A{r}[l]

    A{r}[l]= (1)(lr+1) A{l}[r] .

    Mquadx

    Mquadx = 0.

    (u, v)

    M

    quadx Rnp

    u

    Mquadx (u, v) =

    pl=1

    (1)l+vl{l}TA(lv)x {v},

    A(lv)x =|X{l}[r]TX{v}[s]|

    1r,spl=r;v=s

    Mquadx (u, v) =

    pl=1

    ps=1

    s=v

    pr=1

    r=l

    (1)l+vrslX{l}[r]TX{v}[s]

    =

    ps=1s=v

    pl=2

    l1r=1

    (1)l+vrlX{l}[r]TX{v}[s]

    +

    p

    r=2

    r1

    l=1

    (

    1)l+vr

    l X{l}[r]TX{v}[s]s

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    =

    p

    s=1s=v

    p

    l=2l1

    r=1(1)l+vrl X{l}[r]TX{v}[s]

    +

    pl=2

    l1r=1

    (1)r+vrlX{r}[l]TX{v}[s]

    s.

    s=

    n

    p 1

    X{r}[l]TX{v}[s]

    =

    sk=1

    X{r}[l]T k

    X{v}[s]T k

    = (1)lr+1

    sk=1

    X{l}[r]T k X{v}[s]T k= (1)lr+1 X{l}[r]TX{v}[s] .

    M

    quadx n p

    Z

    M

    quad

    Mquad

    = 0

    Rnp

    () =2 n

    2 Mquad

    + Mconst

    n2T Mconst

    + |ZTZ|

    22

    (n2T Mconst

    + |ZTZ|)2M

    const

    T M

    const.

    Mconst

    T

    Mconst

    =

    n

    ps=1

    pr=1

    (1)u+v+r+srs|Z{u}TZ{r}||Z{v}TZ{s}|1u,vp

    M

    const

    T M

    const

    tr

    Mconst

    T

    Mconst

    = n

    pj=1

    pr=1

    (1)rr|Z{j}TZ{r}|2

    .

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    cov(u , v) =

    2 n2mquadu,v + mconstu,v

    n2T Mconst

    + |ZTZ|

    22n

    ps=1

    pr=1(1)u+v+r+srs|Z{u}TZ{r}||Z{v}TZ{s}|(n2T M

    const + |ZTZ|)2

    , u, v= 1, . . . , p ,

    mquadu,v mconstu,v

    tr(()) =

    p

    j=1

    var(

    j)

    =2p

    j=1

    n2{j}TA(jj){j}+ |Z{j}TZ{j}|

    n2T Mconst

    + |ZTZ|

    n2p

    r=1(1)rr|Z{j}TZ{r}|2

    (n2T Mconst

    + |ZTZ|)2

    .

    2 1.5 1 0.5 0 0.5 1 1.5 20

    0.1

    0.2

    0.3

    0.4

    0.5

    0.6

    var(1

    )/

    2

    var(2

    )/

    2

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    () =2 n

    2 Mquad + Mconst

    n2T Mconst

    + |ZTZ|

    22

    (n2T Mconst

    + |ZTZ|)2M

    const

    T M

    const

    = 2

    24221+ 12

    8 66 6 + 3221

    2221(24221+ 12)

    2

    192 144144 108

    =2

    23

    (2221+1)2

    12

    (2221+1)2

    12

    (2221

    +1)2

    12(441+

    221+1)

    (2221

    +1)2

    .

    var(1) 1

    1 :=

    var(1)

    var(1)

    =

    163(22 + 1)3

    var(1) = 0 = 0

    1

    1

    1/

    2

    2/2

    1= 1

    Bias() = E() =

    ZTZ+2T1

    ZTE(y) = ZTZ+2T

    1ZT (Z+ E())

    =

    ZTZ+2T1

    ZT (Z+ PE()) =

    ZTZ+2T1

    ZTZ =

    ZTZ+2T1

    ZTZ+2T 2T = 2(ZTZ+2T)1T

    = 2 MT

    n2T Mconst

    + |ZTZ|

    =

    2 M

    const

    T

    n2T Mconst

    + |ZTZ| Rp1,

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    BiasT()Bias() = 4TT( M

    const)2T

    (n2T Mconst

    + |ZTZ|)2 R.

    Bias() = 2 M

    const

    T

    n2T Mconst

    +

    |ZTZ

    |

    =

    2

    8 66 6

    1 1 1

    0 0 0

    1 01 01 0

    24221+ 12

    .

    =

    1 1

    T

    Bias() =

    2

    2221+12(2+7221)2(2221+1)

    .

    2 1.5 1 0.5 0 0.5 1 1.5 20

    1

    2

    3

    4

    5

    6

    7

    8

    9

    10

    Bias()

    TBias(

    )

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    BiasT()Bias() =144(8 + 28221+ 49441)

    (2221+ 1)2

    .

    1 = 1

    = 0

    MSE() =

    pj=1

    var(j) + BiasT()Bias(),

    pj=1

    var(j) =2

    pj=1

    n2{j}TA(jj){j}+ |Z{j}TZ{j}|

    n2T Mconst

    + |ZTZ|

    n2p

    r=1(1)rr|Z{j}TZ{r}|2

    (n2T Mconst

    + |ZTZ|)2

    BiasT()Bias() = 4TT( M

    const)2T

    (n2T Mconst

    + |ZTZ|)2,

    MSE()

    MSE() MSE()

    MSE() =

    pj=1

    var

    j

    +

    BiasT()Bias()

    ,

    BiasT()Bias()

    =

    4TT( M

    const)2T

    (n2T Mconst

    + |ZTZ|)2

    =43TT( M

    const)2T(n2T M

    const + |ZTZ|)

    (n2T Mconst

    + |ZTZ|)3

    4n5T M

    constTT( M

    const)2T

    (n2T Mconst

    + |ZTZ|)3

    = 43|ZTZ|TT( Mconst)2T

    (n2T Mconst

    + |ZTZ|)3,

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    pj=1

    var(j) =2

    pj=1

    n2{j}TA(jj){j}+ |Z{j}TZ{j}|n2T M

    const + |ZTZ|

    n2p

    r=1(1)rr|Z{j}TZ{r}|2

    (n2T Mconst

    + |ZTZ|)2

    =2p

    j=1

    2n{j}TA(jj){j}(n2T Mconst + |ZTZ|)

    (n2T Mconst

    + |ZTZ|)2

    2nT M

    const

    n2{j}TA

    (jj){j}+ |Z{j}TZ{j}|(n2T Mconst + |ZTZ|)2

    2np

    r=1(1)rr|Z{j}TZ{r}|2

    (n2T Mconst

    + |ZTZ|)(n2T M

    const + |ZTZ|)3

    +4n23T M

    constp

    r=1(1)rr|Z{j}TZ{r}|2

    (n2T Mconst

    + |ZTZ|)3

    =2p

    j=1

    2n|ZTZ|{j}TA(jj){j} 2nT Mconst|Z{j}TZ{j}|

    (n2T Mconst

    + |ZTZ|)2

    2n|ZTZ| 2n23T Mconst

    pr=1(1)rr|Z{j}TZ{r}|2(n2T M

    const + |ZTZ|)3

    = 2n2p

    j=1

    {j}TA(jj){j}|ZTZ| T Mconst|Z{j}TZ{j}|

    (n2T Mconst

    + |ZTZ|)2

    |ZTZ| n2T Mconstpr=1(1)rr|Z{j}TZ{r}|2

    (n2T Mconst

    + |ZTZ|)3

    = 2n2p

    j=1nT M

    consts1(j)

    3 + |ZTZ|s2(j)(n2T M

    const

    + |ZTZ|)3,

    s1(j) :={j}TA

    (jj){j}|ZTZ| T M

    const|Z{j}TZ{j}|

    +

    pr=1

    (1)rr|Z{j}TZ{r}|2

    ,

    s2(j) :={j}TA

    (jj){j}|ZTZ| T M

    const|Z{j}TZ{j}|

    p

    r=1

    (

    1)rr|Z{j}

    TZ{r}|

    2

    .

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    MSE()

    = 2n2

    pj=1

    nT Mconsts1(j)3 + |ZTZ|s2(j)(n2T M

    const + |ZTZ|)3

    +43|ZTZ|TT( Mconst)2T

    (n2T Mconst

    + |ZTZ|)3.

    |ZTZ| >0

    M

    const

    n2T Mconst

    > 0.

    MSE()

    =0

    = 0,

    = 0

    [, ]

    = 0

    [, 0)

    (0, ]

    = 0 >0 [, ]\{0} : MSE()< MSE().

    = 0

    = 0

    = 0

    = 0

    = 0

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    A= [ar,s]1r,sp

    |A{i,j}||A{k,l}| |A{i,l}||A{j,k}| =(1)

    i+j|A| p= 2|A{ik,jl}||A| p 3

    , i =k, j=l,

    A{q,v} R(p1)(p1), q , v = i ,j,k,l A

    q

    v

    A{ik,jl} R(p2)(p2) i

    k

    j

    l

    p= 2

    i ,j,k,l= 1, 2

    i =k

    j=l

    i= j

    k= l

    i =j

    k=l

    (1) i = 1, j = 1, k= 2, l= 2

    (2) i = 2, j = 1, k= 1, l= 2

    (3) i = 1, j = 2, k= 2, l= 1

    (4) i = 2, j = 2, k= 1, l= 1.

    |A{1,1}||A{2,2}| |A{1,2}|2 =a1,1a2,2 a21,2= |A| = (1)i+j|A|

    |A{1,2}|2 |A{1,1}||A{2,2}| =a21,2 a1,1a2,2= |A| = (1)i+j |A|.

    p3

    i A

    (1)i1

    (i 1)

    i

    A A

    (i 1)

    j

    k

    l

    A

    j

    k

    l

    |A| =

    ai,i ai,j ai,k ai,l

    ai,j aj,j aj,k aj,l

    ai,k aj,k ak,k ak,l

    ai,l aj,l ak,l al,l

    aiajakal

    aTi aTj a

    Tk a

    Tl A{ijkl,ijkl}

    ,

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    aq = aq,1, . . . , aq,i1, aq,i+1, . . . , aq,j1 , aq,j+1 , . . .

    . . . , aq,k1, aq,k+1, . . . , aq,l1 , aq,l+1, . . . , aq,p

    R1(p4), q= i,j,k,l.A{ijkl,ijkl} A i j k l

    i

    j

    k

    l

    A{ijkl,ijkl}

    p Rp1

    i

    j

    k

    l

    pT :=p1, . . . , pi1, 0, pi+1, . . . , pj1, 0, pj+1, . . .

    . . . , pk1, 0, pk+1, . . . , pl1, 0, pl+1, . . . , pp i =k, j=l.

    pTAp= p{ijkl}TA{ijkl,ijkl}p{ijkl},

    p{ijkl}T :=

    p1, . . . , pi1, pi+1, . . . , pj1, pj+1, . . .

    . . . , pk1, pk+1, . . . , pl1, pl+1, . . . , pp R1(p4).

    A

    pTAp > 0

    p

    p{ijkl}TA{ijkl,ijkl}p{ijkl}> 0 p{ijkl}

    A{ijkl,ijkl}

    W = [wr,s]1r,sp4 := (A{ijkl,ijkl})1.

    |A| = A{ijkl,ijkl}

    ai,i ai,j ai,k ai,l

    ai,j aj,j aj,k aj,l

    ai,k aj,k ak,k ak,l

    ai,l aj,l ak,l al,l

    aiajakal

    W

    aTi aTj aTk aTl

    =: |W|1

    ai,i ai,j ai,k ai,l

    ai,j aj,j aj,k aj,l

    ai,k aj,k ak,k ak,l

    ai,l aj,l ak,l al,l

    m1,1 m1,2 m1,3 m1,4

    m1,2 m2,2 m2,3 m2,4

    m1,3 m2,3 m3,3 m3,4

    m1,4 m2,4 m3,4 m4,4

    .

    |A{i,j}| = (1)i+j|W|1

    ai,j aj,k aj,lai,k ak,k ak,l

    ai,l ak,l al,l

    a

    j

    akal

    W

    aTi aTk aTl

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    = (1)i+j

    |W|1

    ai,j aj,k aj,l

    ai,k ak,k ak,lai,l ak,l al,l

    m1,2 m2,3 m2,4

    m1,3 m3,3 m3,4m1,4 m3,4 m4,4

    ,

    j

    A{i,j} (1)j1 (j 1)

    i

    A{i,j} A{i,j} (i 1)

    k

    l

    A{i,j}

    k

    l

    (1)i+j2 = (1)i+j

    |A{i,j}||A{k,l}| |A{i,l}||A{j,k}| = (1)i+j+k+l|W|2

    ai,j aj,k aj,lai,k ak,k ak,l

    ai,l ak,l al,l

    m1,2 m2,3 m2,4m1,3 m3,3 m3,4

    m1,4 m3,4 m4,4

    ai,i ai,j ai,kai,j aj,j aj,k

    ai,l aj,l ak,l

    m1,1 m1,2 m1,3m1,2 m2,2 m2,3

    m1,4 m2,4 m3,4

    ai,j aj,j aj,kai,k aj,k ak,k

    ai,l aj,l ak,l

    m1,2 m2,2 m2,3m1,3 m2,3 m3,3m1,4 m2,4 m3,4

    ai,i ai,j ai,lai,k aj,k ak,l

    ai,l aj,l al,l

    m1,1 m1,2 m1,4m1,3 m2,3 m3,4

    m1,4 m2,4 m4,4

    .

    3 3

    |A{i,j}||

    A{k,l}| |

    A{i,l}||

    A{j,k}|

    = (1)i+j+k+l|W|2

    ai,j aj,k

    ai,l ak,l

    m1,2 m2,3

    m1,4 m3,4

    ai,i ai,j ai,k ai,l

    ai,j aj,j aj,k aj,l

    ai,k aj,k ak,k ak,l

    ai,l aj,l ak,l al,l

    m1,1 m1,2 m1,3 m1,4

    m1,2 m2,2 m2,3 m2,4

    m1,3 m2,3 m3,3 m3,4

    m1,4 m2,4 m3,4 m4,4

    = |A{ik,jl}||A|,

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    |A{ik,jl}| = (1)i+j+k+l

    aj,i aj,kal,i al,k

    ajal

    aTi aTk A{ijkl,ijkl}

    = (1)i+j+k+l|W|1

    ai,j aj,k

    ai,l ak,l

    ajal

    W

    aTi aTk

    = (

    1)i+j+k+l

    |W

    |1 ai,j aj,kai,l ak,l

    m1,2 m2,3

    m1,4 m3,4 .

    s1(j) s2(j)

    s:=p

    j=1

    {j}

    TA(jj)

    {j}|ZTZ| T Mconst

    |Z{j}TZ{j}|

    .

    p= 2

    s= 22|ZTZ| |Z{1}TZ{1}|2

    s=1

    2r=1

    (1)r+srs|Z{r}TZ{s}| +21|ZTZ|

    |Z{2}TZ{2}|2

    s=1

    2r=1

    (1)r+srs|Z{r}TZ{s}|.

    2

    s=12

    r=1(1)r+srs|Z{r}TZ{s}| =21|Z{1}TZ{1}| 212|Z{1}TZ{2}|

    +22|Z{2}TZ{2}|

    s= 22|ZTZ| |Z{1}TZ{1}||Z{2}TZ{2}|

    +21|ZTZ| |Z{1}TZ{1}||Z{2}TZ{2}| + 212|Z{1}TZ{1}||Z{1}TZ{2}|

    + 212|Z{2}TZ{2}||Z{1}TZ{2}| 21|Z{1}TZ{1}|2 22|Z{2}TZ{2}|2.

    |ZT

    Z| |Z{1}T

    Z{1}||Z{2}T

    Z{2}| = |Z{1}T

    Z{2}|2

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    s= 21|Z{1}TZ{1}|2 212|Z{1}TZ{1}||Z{1}TZ{2}| +22|Z{1}TZ{2}|2 21|Z{1}TZ{2}|2 212|Z{2}TZ{2}||Z{1}TZ{2}| +22|Z{2}TZ{2}|2

    = 2

    j=1

    2

    r=1

    (1)rr|Z{j}TZ{r}|2

    .

    p= 3

    s

    s=p

    j=1

    |ZTZ|

    p

    s=1s=jp

    r=1r=j(1)r+srs|Z{jr}TZ{js}|

    |Z{j}TZ{j}|p

    s=1

    pr=1

    (1)r+srs|Z{r}TZ{s}|

    =

    pj=1

    |ZTZ| p

    s=1s=j

    pr=1r=j

    (1)r+srs|Z{jr}TZ{js}| |Z{j}TZ{j}|

    2j |Z{j}TZ{j}| + 2pr=1

    r=j

    (1)r+jrj|Z{j}TZ{r}|

    +

    ps=1s=j

    pr=1r=j

    (1)r+srs|Z{r}TZ{s}|

    =

    pj=1

    2j |Z{j}TZ{j}|2 2|Z{j}TZ{j}| p

    r=1r=j

    (1)r+j rj|Z{j}TZ{r}|

    +

    ps=1

    s=j

    pr=1

    r=j

    (1)r+srs|ZTZ||Z{jr}TZ{js}| |Z{j}TZ{j}||Z{r}TZ{s}|

    .

    i= j

    k= r

    l= s

    |ZTZ||Z{jr}TZ{js}| |Z{j}TZ{j}||Z{r}TZ{s}| = |Z{j}TZ{r}||Z{j}TZ{s}|

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    s=

    p

    j=1

    2j |Z{j}TZ{j}|2 2|Z{j}TZ{j}|p

    r=1r=j

    (1)r+j

    rj |Z{j}T

    Z{r}|

    ps=1s=j

    pr=1r=j

    (1)r+srs|Z{j}TZ{r}||Z{j}TZ{s}|

    = p

    j=1

    ps=1

    pr=1

    (1)r+srs|Z{j}TZ{r}||Z{j}TZ{s}|

    = p

    j=1 p

    r=1(1)rr|Z{j}TZ{r}|

    2

    ,

    Z p 2p

    j=1

    s1(j) =

    pj=1

    {j}

    TA(jj)

    {j}|ZTZ| T Mconst

    |Z{j}TZ{j}|

    +

    pr=1

    (1)rr|Z{j}TZ{r}|2= 0

    pj=1

    s2(j) =

    pj=1

    {j}TA(jj){j}|ZTZ| T Mconst|Z{j}TZ{j}|

    pr=1

    (1)rr|Z{j}TZ{r}|2

    = 2p

    j=1

    pr=1

    (1)rr|Z{j}TZ{r}|2

    .

    MSE()

    MSE()

    = 4n2

    pj=1

    |ZTZ| pr=1(1)rr|Z{j}TZ{r}|2 (n2T M

    const + |ZTZ|)3

    +43|ZTZ|TT( Mconst)2T

    (n2T Mconst

    + |ZTZ|)3.

    pj=1

    var(j) = 4n2p

    j=1

    |ZTZ| pr=1(1)rr|Z{j}TZ{r}|2 (n2T M

    const + |ZTZ|)3

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    BiasT()Bias()

    = 4

    3|ZTZ|TT( Mconst)2T(n2T M

    const + |ZTZ|)3

    .

    Z Rnp, n > p, p 2

    = 0 > 0 [, ]\{0} : MSE()< MSE().

    Z

    [, ]

    [, ]

    MSE()

    = 4n2

    pj=1

    |ZTZ| pr=1(1)rr|Z{j}TZ{r}|2 (n2T M

    const + |ZTZ|)3

    + O(3)

    (n2T Mconst

    + |ZTZ|)3.

    |ZTZ| > 0 pj=1 pr=1(1)rr|Z{j}TZ{r}|2 > 0 MSE()

    = 0

    MSE()

    >0, [, 0)0, = 0

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    Z

    T

    Z

    Z

    T

    Z

    1= . . .= p= 0

    = 0 p

    j=1

    pr=1

    (1)rr|Z{j}TZ{r}|2

    >0

    = 0

    1= 0

    2,3= npj=1pr=1(1)rr|Z{j}TZ{r}|2

    TT( Mconst

    )2T.

    Z

    limMSE() =

    2

    pj=1

    T{j} A

    (jj){j}

    T Mconst

    +

    TT( Mconst

    )2T

    n2 T Mconst

    2 .

    1= 0 2= . . .= p= 0

    pj=1

    s2(j) = 221|ZTZ|p

    j=1

    |Z{1}TZ{j}|2

    TT( Mconst

    )2T= n24

    1

    2

    1

    p

    j=1 |

    Z{1}

    TZ{j}|2 >0

    2=

    2

    n2121

    3=

    2

    n2121

    .

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    MSE() =2

    23

    (22

    2

    1+ 1)2

    +12(

    441+221+ 1)

    (22

    2

    1+ 1)2

    +14

    4(8 + 28221+ 49441)

    (2221+ 1)2

    = 1

    12

    142 + 62221+ 6

    2441+ 24441+ 84

    661+ 147881

    (2221+ 1)

    2 .

    2 =21 = 1

    2,3=

    1

    3= 0.5774.

    MSE() = () + Bias()BiasT()

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    MtxMSE() =2(ZTZ+2T)1ZTZ(ZTZ+2T)1

    +4(ZTZ+2T)1TTT(ZTZ+2T)1

    = (ZTZ+2T)1

    2ZTZ+4TTT

    (ZTZ+2T)1.

    := MtxMSE() MtxMSE() 0

    MtxMSE() =2(ZTZ)1

    2

    ZTZ1 (ZTZ+2T)1 2ZTZ

    +4TTT

    (ZTZ+2T)1 0.

    2 ZTZ+2T Z

    TZ1

    ZTZ+2T 2ZTZ 4TTT 0

    2

    ZTZ+ 22T +4T

    ZTZ1

    T

    2ZTZ 4TTT 0

    2 22Ip 2TTT +24T ZTZ1 T 0.

    0

    22 n2

    ps=1

    pr=1

    rsrs

    0.

    T

    T =n

    p

    r=11r1r . . .p

    r=11rpr

    pr=1pr1r . . . pr=1prpr

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    T

    TT= n2

    pr=1ps=121rsrs . . .pr=1ps=11prsrs

    pr=1

    ps=11prsrs . . .

    pr=1

    ps=1

    2prsrs

    =n

    pr=1

    ps=1

    rsrsT

    .

    22T 2TTT=

    22 n2p

    r=1p

    s=1rsrs

    T.

    c:=

    22 n2ps=1pr=1rsrs 0

    pTTp 0,

    pTcTp= cpTTp 0

    p

    Rp1

    ZTZ

    1 = 12 12

    ZTZ

    ZTZ

    1=

    VVT1

    =V1VT =

    1

    2 VTT

    1

    2 VT

    pT

    cT +24T

    ZTZ1

    T

    p

    =cpTTp +24pT

    12 VTT

    T 1

    2 VTT

    p 0,

    c 0

    c 0

    c

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    j = j

    1

    Sjj

    12

    , j= 1, . . . , p

    0 = y p

    j=1

    j Xj .

    0

    0 = y 1 X1 . . . p Xp

    j =

    j

    1

    Sjj

    12

    , j= 1, . . . , p .

    =+ QD1 R(p+1)1,

    =

    y, 0, . . . , 0T R(p+1)1,

    Q=

    X1 X2 . . . Xp1 0 . . . 0

    0 1 . . . 0

    0 0 . . . 1

    R

    (p+1)p

    D=

    S11

    Spp

    Rpp.

    Bias() = E(QD1+) = QD1E() + E() .

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    E() =

    0+1 X1+. . .+pXp

    0

    0

    01

    p

    =

    1 X1+. . .+p Xp

    1

    p

    = Q{0}

    T{0} = 1, . . . , p {0} = D1

    Bias() =QD1E() QD1

    =QD1Bias().

    () = (QD1+) =QD

    1()D1QT

    MSE() = tr

    QD1()D1QT

    + BiasT()D

    1QTQD1Bias()

    = tr

    D1QTQD1()

    + BiasT()D1QTQD1Bias().

    QTQ=

    X21 + 1 X1X2 . . . X1 Xp

    X1 X2 X22 + 1 . . .

    X2 Xp

    X1Xp X2Xp . . . X2

    p + 1

    =

    X21 X1 X2 . . . X1 Xp

    X1X2 X22 . . .

    X2 Xp

    X1Xp X2 Xp . . . X2

    p

    + Ip

    =

    X1

    Xp

    X1, . . . , Xp + Ip=: XXT + Ip

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    D1 XXTD1 =

    X21S11

    X1

    X2S11S22 . . .

    X1

    XpS11Spp

    X1 X2S11

    S22

    X22S22

    . . . X2 Xp

    S22

    Spp

    X1 XpS11

    Spp

    X2 XpS22

    Spp

    . . .X2pSpp

    ,

    MSE() = tr

    D1( XXT + Ip)D1()

    + Bias()TD1( XXT + Ip)D1Bias()

    = tr

    D1 XXTD1()

    + tr

    D2()

    + Bias()TD1 XXTD1Bias() + Bias()

    TD2Bias().

    {0}:=

    1, . . . ,

    p

    {0}

    pj=1

    var(j) = tr

    (D1)

    = tr

    D1()D1= tr D2() .

    Q {0}

    Bias({0}) =D

    1Bias().

    MSE({0}) = tr

    D2()

    + Bias()

    TD2Bias()

    =

    pj=1

    var(j)

    Sjj+ Bias()

    TD2Bias()

    MSE(0) = tr

    D1 XXTD1()

    + Bias()TD1 XXTD1Bias()

    =

    pj=1

    pi=1

    Xi XjSii

    Sjjcov(i ,

    j)

    +4TT M

    constD1 XXTD1 M

    const

    T

    (n2T Mconst

    + |ZTZ|)2.

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    X

    = 0 >0 [, ]\{0} : MSE()< MSE().

    {0}

    MSE({0}) =

    pj=1

    var(

    j)Sjj

    +

    BiasT()D

    2Bias()

    .

    pj=1

    var(j)

    Sjj= 4n2

    pj=1

    |ZTZ| pr=1(1)rr|Z{j}TZ{r}|2 Sjj (n2

    T Mconst

    + |ZTZ|)3

    BiasT()D

    2Bias()= 43|ZTZ|TT MconstD2 MconstT

    (n2

    T

    M

    const

    + |ZT

    Z|)3

    .

    MSE(

    {0})

    =0

    = 0.

    [1, 1]\{0} 1

    MSE({0}) = 4n2|ZTZ|

    pj=1

    pr=1(1)rr|Z{j}TZ{r}|

    2Sjj (n2

    T Mconst

    + |ZTZ|)3

    + O(3

    )(n2T M

    const + |ZTZ|)3

    .

    pr=1

    (1)rr|Z{j}TZ{r}|2

    >0

    (n2T Mconst

    + |ZTZ|)3 >0 Z Sjj

    Sjj >0

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    var(

    0

    ) = 2p

    j=1

    p

    i=1

    (

    1)i+j Xi Xj

    SiiSjj

    n2{i}TA

    (ij){j}+ |Z{i}TZ{j}|

    n2T Mconst + |ZTZ|

    n2p

    s=1

    pr=1(1)r+srs|Z{i}TZ{r}||Z{j}TZ{s}|n2T M

    const + |ZTZ|

    2

    =2p

    j=1

    pi=1

    (1)i+j XiXjSii

    Sjj

    2n{i}TA

    (ij){j}

    n2T M

    const + |ZTZ|

    n2T Mconst

    + |ZTZ|2

    2nT Mconst

    n2{i}TA

    (ij){j}+ |Z{i}TZ{j}|n2T Mconst + |ZTZ|2

    2np

    s=1

    pr=1(1)r+srs|Z{i}TZ{r}||Z{j}TZ{s}|n2T M

    const + |ZTZ|

    2

    +4n23T M

    constp

    s=1

    pr=1(1)r+srs|Z{i}TZ{r}||Z{j}TZ{s}|

    n2T Mconst

    + |ZTZ|3

    = 2n2p

    j=1p

    i=1(1)i+j

    XiXjSiiSjj

    {i}TA(ij){j}|ZTZ| |Z{i}TZ{j}|T Mconst

    n2T Mconst

    + |ZTZ|2

    |ZTZ| n2T Mconst

    n2T Mconst

    + |ZTZ|3

    p

    s=1p

    r=1(1)r+srs|Z{i}TZ{r}||Z{j}TZ{s}|

    .

    [2, 2]\{0} 2

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    var(0) = 2n2

    |ZTZ

    |

    p

    j=1p

    i=1(1)i+j

    Xi Xj

    SiiSjj{i}TA(ij){j}|ZTZ| |ZT{i}Z{j}|T Mconst

    n2T Mconst

    + |ZTZ|3

    p

    s=1

    pr=1(1)r+srs|Z{i}TZ{r}||Z{j}TZ{s}|

    n2T Mconst

    + |ZTZ|3

    + O(3)

    n2T Mconst + |ZTZ|3

    Bias(0)

    TBias(0) =43|ZTZ|TT MconstD1 XXTD1 MconstT

    (n2T Mconst

    + |ZTZ|)3

    = O(3)

    n2T Mconst

    + |ZTZ|3 .

    MSE(0)=0 = 0.

    [2, 0)

    (0, 2] MSE({0})

    MSE() = 0

    s+ :=

    pj=1

    pi=1

    (1)i+j Xi Xj

    Sii

    Sjj

    |ZTZ|{i}TA

    (ij){j}

    |Z{i}TZ{j}|T Mconst

    .

    p 3

    s+ =

    pj=1

    pi=1

    (1)i+j Xi Xj

    Sii

    Sjj

    |ZTZ| p

    s=1

    s=j

    pr=1

    r=i

    (1)r+srs|Z{ir}TZ{js}|

    |Z{i}TZ{j}|p

    s=1

    pr=1

    (1)r+srs|Z{r}TZ{s}|

    .

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    p

    s=1p

    r=1(1)r+srs

    |Z

    {r

    }

    TZ

    {s

    }|= (

    1)i+jij

    |Z

    {i

    }

    TZ

    {j

    }|+

    ps=1s=j

    (1)i+sis|Z{i}TZ{s}|

    +

    pr=1r=i

    (1)r+jrj|Z{r}TZ{j}| +ps=1s=j

    pr=1r=i

    (1)r+srs|Z{r}TZ{s}|

    s+

    =

    pj=1

    pi=1

    (1)i+j

    XiXjSiiSjj (1)i+jij|Z{i}TZ{j}|2

    |Z{i}TZ{j}|ps=1s=j

    (1)i+sis|Z{i}TZ{s}|

    |Z{i}TZ{j}|pr=1r=i

    (1)r+jrj|Z{r}TZ{j}|

    +

    p

    s=1s=j

    p

    r=1r=i

    (

    1)r+srs |Z

    TZ

    ||Z{

    ir

    }

    TZ{js

    }| |Z{

    i

    }

    TZ{j

    }||Z{

    r

    }

    TZ{

    s

    }| .

    s+ =

    pj=1

    pi=1

    (1)i+j XiXj

    Sii

    Sjj

    (1)i+jij|Z{i}TZ{j}|2

    |Z{i}TZ{j}|p

    s=1s=j(1)i+sis|Z{i}TZ{s}|

    |Z{i}TZ{j}|pr=1r=i

    (1)r+jrj|Z{r}TZ{j}|

    ps=1s=j

    pr=1r=i

    (1)r+srs|Z{i}TZ{s}||Z{j}TZ{r}|

    = p

    j=1

    pi=1

    (1)i+j XiXj

    Sii

    Sjj

    ps=1

    pr=1

    (1)r+srs|Z{i}TZ{s}||Z{j}TZ{r}|

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    =

    p

    i=1p

    s=1(1)i+s

    Xi

    Siis

    |Z

    {i

    }

    TZ

    {s

    }|

    p

    j=1p

    r=1(1)j+r

    XjSjj r|Z{j}TZ

    {r

    }|

    =

    ps=1

    pi=1

    (1)i+sXi

    Siis|Z{i}TZ{s}|

    2.

    p= 2

    s+ =2

    j=1

    2i=1

    (1)i+j Xi Xj

    Sii

    Sjj

    |ZTZ| 2

    s=1s=j

    2r=1r=i

    rs

    |Z{i}TZ{j}|2

    s=1

    2r=1

    (1)r+srs|Z{r}TZ{s}| .

    p= 2

    2s=1

    s=j

    2r=1

    r=i

    rs|ZTZ| (1)r+s|Z{i}TZ{j}||Z{r}TZ{s}|

    =2

    s=1s=j

    2r=1r=i

    rs

    (1)i+j+r+s|ZTZ| (1)r+s|Z{i}TZ{j}||Z{r}TZ{s}|

    = 2

    s=1s=j

    2r=1r=i

    (1)r+srs|Z{i}TZ{s}||Z{j}TZ{r}|.

    s+

    p = 2

    pj=1

    pi=1

    ps=1

    pr=1

    (1)i+j+r+s XiXjSii

    Sjjrs|Z{i}TZ{r}||Z{j}TZ{s}|

    =

    p

    j=1p

    i=1p

    s=1p

    r=1(1)i+j+r+s

    Xi Xj

    SiiSjj rs|Z{i}TZ

    {s

    }||Z{j

    }TZ

    {r

    }|

    =

    pi=1

    ps=1

    (1)s+iXi

    Siis|Z{i}TZ{s}|

    pj=1

    pr=1

    (1)r+j Xj

    Sjjr|Z{j}TZ{r}|

    =

    pi=1

    ps=1

    (1)i+sXi

    Siis|Z{i}TZ{s}|

    2

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    var(

    0) = 4n2

    |ZT

    Z|ps=1

    pi=1(1)i+s

    XiSii

    s|Z{i}TZ{s}|2

    n2T M

    const + |ZTZ|3

    + O(3)

    n2T Mconst

    + |ZTZ|3

    Z

    MSE(0) = 4n2|ZTZ|

    ps=1

    pi=1(1)i+s

    XiSii

    s|Z{i}TZ{s}|2

    n2T M

    const + |ZTZ|

    3

    + O(3)n2T M

    const + |ZTZ|

    3 .

    t:=

    ps=1

    pi=1

    (1)i+sXi

    Siis|Z{i}TZ{s}|

    2 0

    t= 0

    t > 0

    2

    MSE(

    0)

    [2, 0) (0, 2]

    :=

    min(1, 2) , t >01 , t= 0

    Z

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    X

    X=

    1 x1,1 . . . x1,p

    1 xn,1 . . . xn,p

    Rn(p+1).

    =

    (X+)T (X+)1

    (X+)T y.

    = 2

    M

    quad

    x +

    M

    lin

    x +

    M

    const

    x2TAx + 2b

    Tx + |XTX| (X+

    )T y

    =2( M

    quadx X

    Ty + Mlinx

    Ty) +( Mlinx X

    Ty + Mconstx

    Ty) + Mconstx X

    Ty

    2TAx + 2bTx + |XTX|

    .

    X

    |X[j]TX[j]| = |XTX[j]| = 0, j = 2, . . . , p

    |X[1]TX[1]| = |XTX[1]| = |XTX|.

    bTx =|XTX| 0 . . . 0

    R1p,

    Ax=

    |XTX| 0 . . . 00 0 . . . 0

    0 0 . . . 0

    Rpp.

    |Mx| =2|XTX|21+ 2|XTX|1+ |XTX|= |XTX|(221+ 21+ 1).

    |X{u}TX{v}[r]| = 0, v=r = 1

    |X{u}[r]TX{v}[s]

    |= 0, v

    =s

    = 1

    u

    =r

    = 1.

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    b(uv)x T{v} = |X{u}TX{v}[1]| 0 . . . 0 {v}=1|X{u}TX{v}[1]|, v= 1,

    b(u1)x

    T{1} =|X{u}TX{1}[2]| . . . |X{u}TX{1}[p]|

    {1}

    =

    pr=2

    r|X{u}TX{1}[r]|,

    T{1} A(11)x {1}= {1}

    T|X{1}[2]

    TX{1}[2]

    | . . .

    |X{1}[2]

    TX{1}[p]

    |

    |X{1}[p]TX{1}[2]| . . . |X{1}[p]TX{1}[p]|

    {1}

    =

    pr=2

    2r |X{1}[r]TX{1}[r]| + 2p

    s=3

    s1r=2

    rs|X{1}[r]TX{1}[s]|,

    {u}TA

    (uv)x {v}= {u}

    T

    |X{u}[1]TX{v}[1]| 0 . . . 00 0 . . . 0

    0 0 . . . 0

    {v}

    =21|X{u}[1]TX{v}[1]|, u, v= 1,

    {1}TA

    (1v)x {v}= {1}

    T

    |X{1}[2]TX{v}[1]| 0 . . . 0|X{1}[3]TX{v}[1]| 0 . . . 0

    |X{1}[p]TX{v}[1]| 0 . . . 0

    {v}

    =1

    pr=2

    r|X{1}[r]TX{v}[1]|, v= 1,

    {u}TA

    (u1)x {1}= {u}

    T

    |X{

    u

    }[1]

    TX{1

    }[2]

    | . . .

    |X{

    u

    }[1]

    TX{1

    }[p]

    |0 . . . 0

    0 . . . 0

    {1}

    =1

    pr=2

    r|X{u}[1]TX{1}[r]|, u = 1.

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    X

    u = 1M

    quadx X

    T + Mlinx

    T1up1vn

    =21

    M

    constx X

    T1up1vn

    ,

    Mlinx X

    T + Mconstx

    T1up1vn

    = 21

    M

    constx X

    T1up1vn

    .

    (u, v)

    Mquad

    x XT

    Rpn

    u = 1

    Mquadx X

    T(u, v) =

    pr=1

    (1)u+rxv,r{u}TA(ur)x {r}

    = (1)u+1xv,1{u}TA(u1)x {1}+

    pr=2

    (1)u+rxv,r{u}TA(ur)x {r}

    = (1)u+11xv,1p

    r=2

    r|X{u}[1]TX{1}[r]|

    +21p

    r=2

    (1)u+rxv,r|X{u}[1]TX{r}[1]|.

    Mquadx X

    T(u, v) = (1)u+11p

    r=2

    r|X{u}TX{1}[r]|

    +21

    pr=2

    (1)u+rxv,r|X{u}TX{r}|

    =1

    pr=2

    (1)u+r+1r|X{u}TX{r}| +21p

    r=2


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