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IE 212: Computational Methods for Industrial Engineering

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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  1. IE 212: Computational Methods for Industrial Engineering Lecture Notes #4 Appendix: VBA Functions Dr. J. David Porter Summer 2014

  2. 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)

  3. 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

  4. 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)

  5. 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)

  6. 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”

  7. 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

  8. 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

  9. 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)

  10. 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

  11. 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

  12. 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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