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CS 105

Functions, IF FunctionsCS 105

Functions, IF Functions

What is a function?

What is an IF function? A PMT function?

What is a condition?

What is nesting?

CS 105 Spring 2010

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Functions Functions

• An Excel command that does a specific task

• Here’s a common function in Excel:

SUM(A2:B5)• This function’s task: sum all cell values

described within the parentheses (here, the range A2:B5)– the answer is called the function’s return

value

• Why functions? Define once, use many times– simply change the stuff within parentheses– called the arguments of the function

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Arguments

Arguments

• A function has a name and arguments• Arguments can be data, cell names/ranges or

other functions• Examples:

SQRT (9) one argument

AVERAGE (A3, A5, A7) three arguments

SUM (A1:A10, Totals) two arguments (a range

and the name of a range)

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Built-in functionsBuilt-in functions

• Excel comes pre-loaded with many useful functions

• Categories include:– Math & Trig e.g., SQRT, ABS, COUNT, COUNTA,…– Statistical e.g., AVG– Financial e.g. PMT– Text e.g. CONCATENATE

• Later, we will see how to write our own functions to extend Excel’s “toolkit” or “library”

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PMT function

• PMT function requires interest rate/period, number of payments, and amount of loan

• Establish PMT– Amount of loan

– Down payment

– Interest rate/12

– Term (in months)

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As in…

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Note:

• Watch out! Repayment is by default from the bank’s point of view (returns a negative number, and we want a positive number).

• In order to find our payment, we make the final number negative

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Quiz on PMT

• Say the interest on a car is 18% a year. In calculating the interest PER MONTH you:

A. Pay 18% interest each monthB. Pay 18% divided by 12 C. Pay 18% multiplied by 12

CS 105 Spring 2010

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Using Goal Seek • I want to pay only $200 a month. What car can I afford?– Change payment

total by changing one of the above variables

– The top value must have a formula in it

– Goal: $200– Computer calculates

the value of the car you can afford

Data Tab inExcel 2007

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• Suppose we want formula #1 under some conditions, and a different formula #2 under other conditions

• Example: How does the ABS function work?• ABS(A5) = A5 if A5 >= 0, but• ABS(A5) = -A5 if A5 < 0

• Visually:

CS 105 Spring 2010

IF: adding power to functions

True

A5 >= 0

If

False

A5 -A5

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The IF function

Apply formula #1 (after first comma)

True

Apply formula #2(after second comma)

Condition

If

False

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How the IF function works: How the IF function works:

eg, single IF statement looks like this:

IF(A2>90, “A”, “B”)

IF (logical test, value if true, value if false)

Note: string data in a formula must be surrounded by “ ”, why?

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Commission example

If TEESALES sells $100,000 worth of tee shirts, the sales commission rate will be 6%. If the sales total is less than $100,000, the rate will be only 5%.

Finding the Commissionfor sales >= $100,000, pay 6% of salesfor sales < $100000, pay 5% of sales

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Example IF function wizard

Example IF function wizard

An IF function tests for a condition

You can type the IF function directly in the formula box or use the dialog box of the IF Function

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Example of IF Example of IF

=IF(B3>=100000, .06*B3, .05* B3)

B3>=100000?

.06*B3

TRUE

.05*B3

FALSE

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Nested IFsNested IFs

• If TEESALES sells $100,000 worth of tee shirts, the sales commission rate will be 6%.

• If the sales total is equal to or more than $80,000, but less than $100,000, the rate will be 5%.

• If total sales are below $80,000, the rate will be 3.5% of sales.

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Example 2 of IF Example 2 of IF

B3>=100000?

.06*B3

.035* B3

TRUE

FALSE? Then another test...

.05*B3

TRUE FALSE

=IF( B3>=100000, .06*B3, IF(B3>=80000, .05*B3, .035*B3) )

B3>=80000?

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Practice with Relational Operators Practice with Relational Operators

• A1 = B1 -- FALSE• A1 <> B1 -- TRUE

• A1 = B2 -- FALSE• A1 < B1 -- TRUE

• A1 < B2 -- TRUE• A1 = A2 -- TRUE

• A1 >= A2 -- TRUE• A2 > B2 -- FALSE

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AND, OR, NOT Functions

Formula view

Output of formulas:

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COUNTIF Function

• Syntax: COUNTIF(Range, Criteria)• Can be used on a summary worksheet, as in

lab

Download employee.xls to practice this

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SUMIF Function

• The SUMIF function adds figures to a total only if they match a certain criterion

• The syntax is SUMIF( range, criteria to check, range where numbers are)

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Text Functions• Concatenation (putting two words together)

• Concatenation can be done by a function– e.g. =CONCATENATE(B3,C4)

• Operands can be :

– character strings: “Tarzan” & “Jane”– cell addresses containing text values:

B3• Concatenation can also be done by using an operator &

e.g. = B3 & C4

CS 105 Spring 2009

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Adding a space

• Strings in formulas must always appear in quotes in Excel.

• To add a space, just put it between quotes. • Remember, there is an ASCII value for a

space!• You can also put a space between the quote

and the start of WaterCS 105 Spring 2009

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To Summarize

• What is a function?

• What is an IF function? A PMT function?

• What is a condition?

• What is nesting?