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Lesson 7 Mathematical Functions


Mathematical functions are Excel 2010 VBA built-in functions. Some of the Math functions are Int, Sqr, aAs, Exp, Log, Sin, Cos, Tan , Atn, Fix , Rnd and Round.

a) Rnd is the function that generates random numbers between 0 and 1.

b) Int is the function that converts a number into an integer by truncating its decimal part and the resulting integer is the largest integer that is smaller than the number. For example, Int(2.4)=2, Int(4.8)=4, Int(-4.6)= -5, Int(0.032)=0 and so on.

c) Sqr is the function that computes the square root of a number. For example, Sqr(4)=2, Sqr(9)=2 and etc.

d) Abs is the function that returns the absolute value of a number. So Abs(-8) = 8 and Abs(8)= 8.

e) Exp of a number x is the value of ex. For example, Exp(1)=e^1 = 2.7182818284590

f) Fix and Int is the same if the number is a positive number as both truncate the decimal part of the number and return an integer. However, when the number is negative, it will return the smallest integer that is larger than the number. For example, Fix(-6.34)= -6 while Int(-6.34)=-7.

g) Round is the function that rounds up a number to a certain number of decimal places. The Format is Round (n, m) which means to round a number n to m decimal places. For example, Round (7.2567, 2) =7.26

h) Log is the function that returns the natural Logarithm of a number. For example,Log (10)= 2.302585

We shall learn how to implement these functions in the following examples.

Example 7.1

The example demonstrate how to generate random numbers between 0 and 1 using the rnd function.

Private Sub CommandButton1_Click()
 For x = 1 To 10
  MsgBox Rnd
 Next x
End Sub

Example 7.2

In this example, Int(Rnd*6) will generate a random integer between 0 and 5 because the function Int truncates the decimal part of the random number and returns an integer. After adding 1, you will get a random number between 1 and 6 every time you click the command button. For example, let say the random number generated is 0.98, after multiplying it by 6, it becomes 5.88, and using the integer function Int(5.88) will convert the number to 5, and after adding 1 you will get 6.

Private Sub Commandbutton1_Click ( )
 Num=Int(Rnd*6)+1
 MsgBox Num
End Sub

Example 7.3

This program will find the square root of number 1 to 10 and displays them on the message box when the user clicks on the OK button.

 Private Sub CommandButton1_Click()
 For i = 1 To 10
  MsgBox Sqr(i )
 Next
End Sub
 

Example 7.4

This VBA program computes the values of Int(x), Fix(x), Round(x,4) and Log(x) and displays them in respective cells. Notice that you can combine two or more functions in your code, like Round(Log(x)). It uses the Do Loop statement and the Rnd function to generate random numbers. The statement x = Rnd * 7 generate random numbers between 0 and 7 . Using commas in between items will create spaces between them and hence a table of values can be created. The program is shown below and the output is shown in Figure 7.1:

Private Sub CommandButton1_Click()
Dim n As Integer
Dim x As Single
 n = 2
Do While n < 12
 x = Rnd * 7

 Cells(n, 1) = x
 Cells(n, 2) = Int(x)
 Cells(n, 3) = Fix(x)
 Cells(n, 4) = Round(Cells(n, 1), 4)
 Cells(n, 5) = Round(Log(x), 4)
 Cells(n, 6) = Round(Sqr(x), 4)
 n = n + 1
Loop
End Sub
Figure 7.1 The Salary Function





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