LSP 121. LSP 121 Math and Tech Literacy II. Topics. More VBA. More VBA. Variables

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1 Greg Brewster, DePaul University Page 1 Math and Tech Literacy II Greg Brewster DePaul University Topics More Visual Basic Variables Naming Rules Implicit vs. Explicit Types Variable Lifetime Static variables User Defined Functions IF statements Conditions Branching Variables Variables provide a local storage space to store a value within a VBA subroutine. Variable names Must be made up of letters, numbers and the underscore character (_) only. Can t be the same as VBA keywords with special meanings such as Sub or End or If, etc.

2 Greg Brewster, DePaul University Page 2 Implicit Variable Types You can declare the type of data stored in a variable using the Dim statement Dim my_var as Integer But you don t have to do this. If you do not declare the variable type, then VBA just guesses what type of data should be stored by how you use it. This is called an implicit variable type Variable Lifetime Normally all variables in a subroutine are reset to zero every time you call your subroutine. If you don t want this reset to happen (so the variable keeps its value between subroutine calls), then add a statement to make the variable static Static my_var User Defined Functions We know that Excel already has lots of built-in functions we can use in a spreadsheet, like Sum(range) to find the sum of a range Stdev(range) to find the standard deviation You can create your own new functions called User Defined Functions (UDFs) to do whatever you need.

3 Greg Brewster, DePaul University Page 3 User Defined Functions You can type in a UDF in the same way that you type in a subroutine, but use the word Function instead of Sub Whatever value you assign to the function name becomes the value returned by the function call. Example Function Roll_Die() This function returns a random number between 1 and 6. It uses two Excel built-in functions rnd() - generates a random value between 0 and 1 int() - returns the integer part of a number Roll_Die = int(rnd() * 6) + 1 End Function Roll_Die Function Once you have typed in the Roll_Die function in VBE, you can use Roll_Die() anywhere in your spreadsheet to get a random value from 1 to 6.

4 User Defined Functions You may want your function to have parameters, which allow you to pass numbers to it when you call it. These go into parentheses after the function name. The parameters in the function definition are just variables that receive the values in parentheses when the function is called. Example Function Add_Squares(first_number, second_number) This function adds together the squares of two numbers Add_Squares = (first_number * first_number) + (second_number * second_number) End Function Add_Squares Function Once you have entered the code for Add_Squares into VBE, then you can call it anywhere, for example: Add_Squares(3, 5) will give back the value 34 (9 + 25) Add_Squares(A3, A4) will give back the sum of squares of values in cell A3 and A4. Greg Brewster, DePaul University Page 4

5 Example: Dice Roll Average As an example, let s implement an Excel subroutine that keeps track of the average of a series of dice rolls On the spreadsheet we will show: The current dice roll (in cell C3) The number of dice rolls so far (in C5) The total of dice rolls so far (in C7) The average dice roll so far (in C9) Example: Dice Roll Average Pseudo Code for each Dice Roll: Assign random value (1-6) to cell C3 Get current value in cell C5, add one to it, and store it back into cell C5 Get current value in cell C7, add C3 to it, and store total back into cell C7 Set C9 = C7 / C5 Example: Dice Roll Average Sub Do_Roll() This subroutine rolls die and computes avg. This_Roll = roll_die() Range( C3 ).Value = This_Roll Num_Rolls = Range( C5 ).Value Range( C5 ).Value = Num_Rolls + 1 Total_Rolls = Range( C7 ).Value Range( C7 ).Value = Total_Rolls + This_Roll Range( C9 ).Value = =C7/C5 End Sub Greg Brewster, DePaul University Page 5

6 IF Statements IF statements allow you to conditionally execute statements based on whether a condition is true or false. 1-way IF Statement The 1-way IF statement looks like this: IF <condition> THEN <statement1> <statement2> Where <condition> is a comparison of two values using =, <, <=, >, >= <statement1>, <statement2>, are executed only if the <condition> is TRUE. IF Example IF Range( C3 ).Value < 5 THEN MsgBox C3 is less than five This will pop up a MsgBox displaying the message C3 is less than five if the value stored in cell C3 is less than 5. Otherwise, nothing happens. Greg Brewster, DePaul University Page 6

7 2-way IF Statement The 2-way IF looks like this: IF <condition> THEN <statementsa> <statementsb> If the <condition> is true, then all statements in <statementsa> are executed. If the <condition> is false, then <statementsb> are executed. IF Example IF Range( C3 ).Value < 5 THEN MsgBox C3 is less than five MsgBox C3 is greater than or equal to five Multi-way IF Statement The Multi-way IF looks like this: IF <condition1> THEN <statementsa> IF <condition2> THEN <statementsb> <statementsd> Greg Brewster, DePaul University Page 7

8 Multi-way IF Statement Only one set of statements will get executed based on the first condition that is true. If <condition1> is true, then <statementsa> are executed. If <condition1> is false and <condition2> is true then <statementsb> are executed. Etc. You can have as many IF parts as you wish, each is checked only if all previous conditions are false. The optional part at the end is executed only if all conditions are false. Example Sub Do_Roll() This subroutine rolls a die, displays the value in cell C3 and displays a message in cell C5 indicating whether it is a 6 Die1 = Roll_Die() Range( C3 ).Value = Die1 IF (Die1 = 6) THEN Range( C5 ).Value = The roll is a six!! Range( C5 ).Value = That is not a six. End Sub Sub Do_Roll2() This subroutine rolls a die, displays the value in cell C3, displays a message in cell C5 indicating whether it is a 6, and displays a count of how many sixes have been rolled so far in cell C7 Static Count_Sixes Die1 = Roll_Die() Range( C3 ).Value = Die1 IF (Die1 = 6) THEN Range( C5 ).Value = The roll is a six!! Count_Sixes = Count_Sixes + 1 Increase value by 1 Range( C7 ).Value = Count_Sixes Range( C5 ).Value = That is not a six. End Sub Greg Brewster, DePaul University Page 8

LSP 121. LSP 121 Math and Tech Literacy II. Topics. Loops. Loops. Loops

LSP 121. LSP 121 Math and Tech Literacy II. Topics. Loops. Loops. Loops LSP 121 Math and Tech Literacy II Greg Brewster DePaul University Topics The FOR loop Repeats a set of statements a fixed number of times The WHILE loop Repeats a set of statements until a condition is