class 3 programming in visual basic. class objectives learn about input/output learn about strings...
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Class Objectives
• Learn about input/output• Learn about strings• Learn about subroutines• Learn about arrays• Learn about Boolean operations
Addressing Spreadsheet Cells
A B C D
1
2 45
3
4
Rows
Cell (2, 3)
R1C1 Reference Style
row, column
Columns
VBA Interaction with Excel
Excel
VBA Function
0, 1, 2, 3 … numbers
1 number
Excel
VBA Subroutine
0, 1, 2, 3 … numbers
1, 2, 3 … numbers
Our focus today
Strings
Sub string_demo() Cells(10, 1) = "First" Cells(10, 2) = "Second" Cells(10, 3) = "Third"End Sub
Using the VBA editor, enter the following program…
While in VBA editor, press F5 to run
SubroutineName
Stringsin double quotes
No arguments passed
Sample Subroutine with Calculation
Sub sum_and_product_of_five_numbers() 'This program gives the sum and product of 'five numbers located in Cells B1 to B5 Dim row As Integer Dim sum, product As Double sum = 0 product = 1 For row = 1 To 5 sum = sum + Cells( row, 2) product = product * Cells( row, 2) Next row Cells(6, 1) = "sum" Cells(7, 1) = "product" Cells(6, 2) = sum Cells(7, 2) = productEnd Sub
Subroutine name
Comment
Declare variables
Initialize variables
Start loop
Input and calculate
End loop
Output
End
In VBA editor, enter this program.
An easier way to execute a subroutine You can link a
subroutine to a keyboard control character.
Assignment is made under Options in the Macro dialog box.
Using Macro Options Under Options, fill in a
letter next to “ctrl+” and the selected macro can be executed by pressing that key combination.
Be careful. If you choose a character that is a standard Windows function (e.g., ctrl+c), VBA will overwrite the Windows function with your macro.
Arrays
Dim list (5) as integer
Example 1
0 4
1 7
2 89
3 8
4 45
5 -3
Indices
Default: Index starts with zero
Numbersstoredinarray
Arrays
Dim list (1 to 5) as integer
1 7
2 89
3 8
4 45
5 -3
Indices
Override: Index starts with one
Numbersstoredinarray
Example 2
Arrays
Dim list (1 to 5, 1 to 2) as integer
1 7 32
2 89 9
3 8 46
4 45 -8
5 -3 8
Row Indices
1 2
Column Indices
This is a two-dimensional array. Up to 60 dimensions are allowed.
Example 3
Sample ProgramSub array_demo() Dim list(1 To 5) As Integer Dim i As Integer Dim sum As Integer sum = 0 i = 1 list(1) = 1 list(2) = 4 list(3) = 9 list(4) = 16 list(5) = 25 Do While sum < 16 sum = sum + list( i) i = i + 1 Loop Cells(15, 1) = "sum =" Cells(15, 2) = sumEnd Sub
Title
Declare variables
Initialize variables
Start loop
Calculate
End loop
Output
EndEnter and run this program.
ResultsSub array_demo() Dim list(1 To 5) As Integer Dim i As Integer Dim sum As Integer sum = 0 i = 1 list(1) = 1 list(2) = 4 list(3) = 9 list(4) = 16 list(5) = 25 Do While sum < 16 sum = sum + list( i) i = i + 1 Loop Cells(15, 1) = "sum =" Cells(15, 2) = sumEnd Sub
Boolean Operations
Truth Tables
A B Y0 0 00 1 01 0 01 1 1
And
A B Y0 0 00 1 11 0 11 1 1
Or
A Y0 11 0
Not
result = expression1 Or expression2
result = Not expression
result = expression1 And expression2
0 = false1 = true
Y A B
Example Program
Option ExplicitSub Boolean_test() Dim truth As Boolean Dim a, b As Integer a = 1 b = 2 truth = False If a = 1 And b = 2 Then truth = True End If Cells(1, 1) = truthEnd Sub
Title
Declare variables
Initialize
Boolean operationAssign
OutputEnd
Enter and run this program. To see what happens, play with various Boolean operators, and different initial values of a and b.
Function Exercise The value of (the ratio of a circle’s circumference to its
diameter) has been estimated for about 4000 years. Several methods for calculating are presented in the Math
Supplement (pages 8-10). Excel’s built in function for is only accurate to 14 decimal
places (van Rooman did better in 1593). As a team, pick ~4 (1 per team member) of the various
methods used to estimate using infinite series (avoid Methods a, c, e and k).
Program your function to calculate the first 50 terms, or stop when the value does not change by more than 10-6.
Subroutine Exercise Convert your function into a subroutine. The subroutine should title Column A as and
Column B as that is, the change in from the previous iteration.
Then beginning in Cells A2 and B2 and going down, output the successive terms of .
Stop the iteration after the first 200 terms, or if an additional term does not change the value of by more than 10-10.
For each method selected by your teammates, compare the rate that they converge to an accurate value of