IE 212: Computational Methods for Industrial Engineering

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# IE 212: Computational Methods for Industrial Engineering - PowerPoint PPT Presentation

IE 212: Computational Methods for Industrial Engineering. Lecture Notes #4 Appendix: VBA Functions. Dr. J. David Porter Summer 2014. String Functions. There are several string functions available in VBA These functions are useful to inspect and manipulate strings

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### IE 212: Computational Methods for Industrial Engineering

Lecture Notes #4 Appendix:

VBA Functions

Dr. J. David Porter

Summer 2014

String Functions
• There are several string functions available in VBA
• These functions are useful to inspect and manipulate strings
• Resulting strings can be used later to create other lists or to concatenate them with other values (i.e., strings or numerical)
• Two useful string functions are UCase and LCase, which can be used to convert a string into all upper case or all lower case, respectively
• UCase(string variable or string expression)
• LCase(string variable or string expression)
String Functions (cont.)
• A very useful string function is Len
• This function determines the length of a string variable value or string expression
• Len(string variable or string expression)
• String manipulation almost always start with determining the length of the string
• Other useful string manipulation functions include
• Left
• Right
• Mid
• Trim
• LTrim
• RTrim
• InStr
• InStrRev
Conversion Functions
• There are several functions in VBA that can be used to convert one data type to another
• Two main conversion functions used with numerical values are CInt and CDbl
• CInt converts a variable to an Integer data type
• CInt(variable or expression)
• CDbl converts a variable to a Double data type
• CDbl(variable or expression)
• The Val function also extracts a numerical value from a string
• The input for this function is an expression
• Val(expression)
Conversion Functions (cont.)
• Any numeric expression can also be converted to a string using the CStr function
• The input for this function is again any variable or expression
• CStr(variable or expression)
• The CDate function converts values into the Date data type
• This data type is necessary to work with dates in your code for comparisons or calculations
• CDate(variable or expression)
Conversion Functions (cont.)
• Two other useful conversion functions are Asc and Chr
• These functions, which use the ASCII list of numbers and characters, can be used to convert letters to numbers and numbers to letters, respectively
• Asc(character)
• Asc(“A”) = 65
• Chr(number)
• Chr(65) = “A”
VBA Math Functions
• We can use typical math functions in VBA without needing to create a formula in the spreadsheet
• Typical Math Functions
• Trigonometric Functions
• Derived Math Functions
• We will describe six basic math functions
• Abs
• Sqr
• Int
• Rnd
• Exp
• Log
Abs and Sqr Functions
• The Abs function calculates the absolute value of a variable
• This function can be used with both Integer and Double data types (as well as with other numerical variables)
• It will return the same data type which is used in the function
• Abs(-10) = 10
• The Sqr function calculates the square root of a number
• It can also be used with any numerical data type
• Must be greater than 0
• It will always return a Double data type
• Sqr(100) = 10
Int and Rnd Functions
• The Int function removes the decimal part of a Double variable and returns the integer part
• The result will be an Integer data type
• For positive numbers, the Int function always rounds down
• For negative numbers, the Int function will return the first negative integer less than or equal to the original variable value
• Int(5.6) = 5
• Int(-4.3) = -5
• The Rnd function will generate a random number
• You can either enter a seed as a parameter for the function, or leave the seed value blank
• This function will return a Doubledata type between 0 and 1
• To create random integers in a specific range, use the formula
• Int((upperbound - lowerbound + 1) * Rnd + lowerbound)
Exp and Log Function
• The Exp function raises the constant e to some power given in the function statement
• The value returned will be a Doubledata type
• Exp(2) = e2 = 7.389056099
• The Log function calculates the natural log (i.e., the logarithm with base e) of a given number
• The result is a Doubledata type
• You can calculate logarithms with base n for any number by dividing the natural logarithm of that number by the natural logarithm of n
• For example, to calculate the log of 15 with base 10 (Log1015), you would type
• Log(15) / Log(10) = 1.176091259
Trigonometric Functions
• There are four basic trig functions that we will describe
• Sin
• Cos
• Tan
• These functions all take angles (in radians) as a parameter
• To convert degrees to radians, multiply degrees by pi/180
• The number p is unavailable in VBA
• However, we know that tan(p/4) = 1
• Therefore, VBA can calculate the value of p by using the formula
• pi = 4 * Atn(1)
• If high precision is not required, you can use Const pi = 3.14159
Sin, Cos, and Tan Functions
• The Sin, Cos, and Tan functions take an angle (in radians) and return the ratio of two sides of a right triangle
• The value returned is a Double data type
• The result of the Sinand Cos functions will be between -1 and 1

Sin(pi/4) = 0.7071067812

Cos(pi/3) = 0.5

Tan(pi/6) = 0.5773502692