Got a version of Excel that uses the menu interface (Excel 97, Excel 2000, Excel 2002, or Excel 2003)? This site is for you! If you use a later version of Excel, visit our ExcelTips site focusing on the ribbon interface.
With more than 50 non-fiction books and numerous magazine articles to his credit, Allen Wyatt is an internationally recognized author. He is president of Sharon Parq Associates, a computer and publishing services company.
Learn more about Allen...
Lars ran into a problem using the ATAN2 function in a macro. He developed a rather complicated set of instructions, only to have VBA generate an error when it tried to use the ATAN2 function. He was able to simplify the macro so he could recreate the problem:
Sub Test() Dim A As Double Dim C As Double Dim E As Double A = 5908 C = 0 C = -C E = 180 / WorksheetFunction.Pi MsgBox E * WorksheetFunction.Atan2(C, A) End Sub
When the code is executed, the error is generated on the line where ATAN2 is executed. Lars was wondering what, exactly, caused the problem.
The problem is apparently related to how you are manipulating the C variable. You first define C as zero, and then negate this value. There is no such thing as negative zero, and when you try to negate the value, Excel apparently balks when that value is subsequently used in the formula.
One way to solve the problem is simply to change the way in which C is transformed to account for zero values. Change the macro so that it looks like this:
Sub Test() Dim A As Double Dim C As Double Dim E As Double A = 5908 C = 0 If C <> 0 Then C = -C E = 180 / WorksheetFunction.Pi MsgBox E * WorksheetFunction.Atan2(C, A) End Sub
Now the macro will work just fine because you are only doing the transform on C if it doesn't equal zero.
It also appears that the error is only generated if C is defined as a floating-point value. If you dimension C as an Integer, then the original macro does not generate an error. This could indicate that the problem is related to how a floating point representation of the non-existent negative zero is internally represented. Since the Integer data type deals strictly with whole numbers, that representation problem does not occur.
You also can get rid of the problem if you declare C as a Variant data type, or if you remove the declaration line altogether (which means that VBA defaults to declaring C as a Variant when it is first used).
ExcelTips is your source for cost-effective Microsoft Excel training. This tip (2892) applies to Microsoft Excel 97, 2000, 2002, and 2003.
Excel Smarts for Beginners! Featuring the friendly and trusted For Dummies style, this popular guide shows beginners how to get up and running with Excel while also helping more experienced users get comfortable with the newest features. Check out Excel 2013 For Dummies today!