Ie 212 computational methods for industrial engineering
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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

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IE 212: Computational Methods for Industrial Engineering

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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

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