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Logarithimic Graphing

Posted by sparkle on February 08, 2002 4:35 PM

I need to be able to customize the scale on semilog graphs with excel; however, Excel only allows the vertical axis to be in powers of 10. My data is often in smaller ranges than this, and I want clients to be able to see smaller delimations than 1, 10, 100 etc. I was wondering if anybody has either a fix for this or has insight into a good VBA program that I could write to fix this problem. Thanx.

Posted by Damon Ostrander on February 09, 2002 12:09 AM

Hi Sparkle,

Yes, I have also chafed under this limitation of the log axes. What I sometimes do, and this permits starting and ending the axis at any point, is to take the log (base 10) of the values you are plotting, and plot these values against a linear axis. This way a value of -1 on the axis will represent 0.1, 0 will represent 1, 1 will represent 10, 2 will represent 100, etc. So now if you want the axis to start with a value of 2, you would actually start it at 0.3 (the log of 2). This means that you will have to label the axis "Log(y)" and the tic marks will be at even increments, but at least the values are correctly plotted against the axis.

I hope this helps.