1. Homework Discussion Homework 4 (Glade Manual Chapter 4) More on Logical, Information and Text Functions

2. Logical operators in Excel ComparisonSymbol Less than< Less than or equal to<= Equal to= Greater than or equal to>= Greater than> Less than or greater than<>

3. Logical functions in Excel Constants TRUE() and FALSE() Traditional Boolean operators NOT(arg), AND(arg1,…), OR(arg1,…) −For Boolean functions, the arguement arg needs to evaluate to TRUE/FALSE

4. Boolean IS (information) functions in Excel Where Ref is a cell reference FunctionTRUE if ISBLANK(Ref)Empty cell ISERR(Ref)Cell has any error except #N/A ISERROR(Ref)Cell has any error ISLOGICAL(Ref)Cell has logical (Boolean) value ISNA(Ref)Cell has #N/A error (Reference not avail.) ISNONTEXT(Ref)Cell is not text, TRUE for blank ISNUMBER(Ref)Cell has a number ISREF(Ref)Cell has a valid cell reference ISTEXT(Ref)Cell has text

5. Text functions in Excel Where Ref is a cell reference and # is a number FunctionOutput LEFT(Ref, #)# leftmost characters from a text value RIGHT(Ref, #)# rightmost characters from a text value MID(Ref, #1, #2)From position #1 in a text value, return #2 characters LEN(Ref)Number of characters in a text string EXACT(Ref1, Ref2)Checks it two strings are identical CONCATENATE(Ref1, …)Joins several text strings into one UPPER(Ref)Converts text to upper case LOWER(Ref)Converts text to lower case TEXT(#, format)Formats # and converts to text (see help for format) VALUE(Ref)Converts text to a number

6. A note on the XOR gate Excel doesn’t have a function to simulate the XOR gate You need to combine other functions to obtain this functionality Two possible ways: −XOR is TRUE when either input is TRUE, AND NOT where both inputs are TRUE, i.e. in Boolean XOR = (A+B)(AB)’  In Excel: XOR=AND( OR(A,B), NOT(AND(A,B)) ) −XOR is TRUE only when the inputs are not equal  In Excel XOR=A <> B