A bit more about variables>> var1 = [ 1 2 3]var1 = 1 2 3

>> var2 = var1var2 = 1 2 3

>> var1 = [4 5 6]var1 = 4 5 6

>> var2var2 = 1 2 3

>> var3 = 'Mostly Harmless'

var3 =

Mostly Harmless

>> var3(2:9)

ans =

ostly Ha

Strings – vectors of characters

Control Structures•Sequence

•Repetition

•Selection

SequencePop1=23

birthRate=0.2

deathRate=0.1

birth=Pop1 * birthRate

death=Pop1 * deathRate

change=birth - death

Pop2=Pop1 + change

(The commands are executed one after the other)

Repetitions

Reminder

function pop = popDynam(popSize1, birthRate, deathRate)

birth = popSize1 * birthRate;

death = popSize1 * deathRate;

change = birth - death;

popSize2 = popSize1 + change;

pop = [popSize2 birth death];end

Please note the indentation.

>> popDynam(23,0.2,0.1)

ans =

25.3000 4.6000 2.3000

>>

popDynam([23 0.2 0.1])

An Alternative approach is to encapsulate the three parameters in a single element – a vector.

function pop=popDynam(popParam)

popSize1 = popParam(1);

birthRate = popParam(2);

deathRate = popParam(3);

birth = popSize1 * birthRate;

death = popSize1 * deathRate;

change = birth - death;

popSize2 = popSize1 + change;

pop = [popSize2 birth death];

end

>> popDynam([23 0.2 0.1])

ans =

25.3000 4.6000 2.3000

>>

The vector [23 0.2 0.1] represents the parameters

of a population.

How would we represent the parameters of three

populations?

popParam = [23 0.2 0.1; 38 0.25 0.05; 17 0.5 0.4]

popParam =

23.0000 0.2000 0.1000 38.0000 0.2500 0.0500 17.0000 0.5000 0.4000

>>

popParam(:,1) population sizepopParam(:,2) birth ratepopParam(:,3) death rate

function pop=popDynam(popParam)

for iPop = 1:3 popSize1 = popParam(iPop,1); birthRate = popParam(iPop,2); deathRate = popParam(iPop,3); birth = popSize1 * birthRate; death = popSize1 * deathRate; change = birth - death; popSize2 = popSize1 + change; pop(iPop,:) = [popSize2 birth death];

endend

function pop=popDynam(popParam)

for iPop = [1 2 3] popSize1 = popParam(iPop,1); birthRate = popParam(iPop,2); deathRate = popParam(iPop,3); birth = popSize1 * birthRate; death = popSize1 * deathRate; change = birth - death; popSize2 = popSize1 + change; pop(iPop,:) = [popSize2 birth death];

endend

What is the output of this function?

function pop=popDynam(popParam)

for iPop = [1 3] popSize1 = popParam(iPop,1); birthRate = popParam(iPop,2); deathRate = popParam(iPop,3); birth = popSize1 * birthRate; death = popSize1 * deathRate; change = birth - death; popSize2 = popSize1 + change; pop(iPop,:) = [popSize2 birth death];

endend

What is the output of this function?

function pop=popDynam(popParam)

for iPop = 1:size(popParam,1) popSize1 = popParam(iPop,1); birthRate = popParam(iPop,2); deathRate = popParam(iPop,3); birth = popSize1 * birthRate; death = popSize1 * deathRate; change = birth - death; popSize2 = popSize1 + change; pop(iPop,:) = [popSize2 birth death];

endend

But the input matrix may be larger….

Selectionif (Pop1>60)

deathRate=0.15

birthRate=0.12

end

If-else-end

if (Pop1>60)deathRate=0.15birthRate=0.12

elsedeathRate=0.1birthRate=0.2

end

If-elseif-endif (Pop1>60)

deathRate=0.15

birthRate=0.12

elseif ((Pop1>40) & (Pop1<61))

deathRate=0.13

birthRate=0.18

else

deathRate=0.1

birthRate=0.2

end

and

Relational operators

<

>

<=

>=

== (equals)

~= (does not equal)

Logical operators

& (and)~ (not)| (or)

e.g.,:if ((A>B) | (B~=C))

Logical expressions cab be interpreted

>> 10 > 1

ans =

1

>> 10 > 100

ans =

0

Logical expressions cab be applied to vectors and matrices

>> popParam popParam = 23.0000 0.2000 0.1000 38.0000 0.2500 0.0500 17.0000 0.5000 0.4000

>> popParam(:,1) > 30ans = 0 1 0

The “find” command>> popParam popParam = 23.0000 0.2000 0.1000 38.0000 0.2500 0.0500 17.0000 0.5000 0.4000

>> find( popParam(:,1) > 30)ans = 2

Repetition with logical condition>> i = 10;>> while (i > 0) disp(1/i); i = i - 1; end 0.1000 0.1111 0.1250 0.1429 0.1667 0.2000 0.2500 0.3333 0.5000 1>>

commands

output

A bug>> i = 10;>> while (i < 11)

disp(1/i);i = i - 1;

end

commands

A bug>> i = 10;>> while (i < 11)

disp(1/i);i = i - 1;

end 0.1000 0.1111 0.1250 0.1429 0.1667 0.2000 0.2500 0.3333 0.5000 1 Inf -1 -0.5000 -0.3333

commands

>> i = 10;>> while (i < 11)

disp(1/i);if (isinf(1/i))

error('Bad number');endi = i - 1;

end 0.1000 0.1111 0.1250 0.1429 0.1667 0.2000 0.2500 0.3333 0.5000 1 Inf??? Bad number