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 log10 scale and negative values

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erciyes38 Posted - 10/22/2009 : 07:13:52 AM
Origin Ver. OriginPro8
Operating System: Win.Xp

I need to plot my data in log10 x scale.But, my data points are negative value points.

are any way to solution of the problem?
2   L A T E S T    R E P L I E S    (Newest First)
erciyes38 Posted - 10/27/2009 : 11:44:52 AM
thanks a lot for your help...

nicely.
larry_lan Posted - 10/23/2009 : 01:29:25 AM
Hi:

Mathematically, what's the value of log(-1)? So it's impossible to use the real logarithm axis.

So I supposed your data is in a really wide range and you want to plot them tight. An workaround as below:



Column A and B are raw data, and the other columns are:

Col(C) = -log(-Col(A));
Col(D) = Col(B);

And Column E is just the same data from Column A, but sort ascendingly. Then we will use this column E as axis ticks. Plot column C & D, and double-click the X axis to bring up X Axis property dialog. On Tick Labels tab, use Tick-indexed dataset Type and assign column E to Dataset drop down:



Then you will get something like:



Note that it's not really log scale. The scale still linear, but we use different tick labels.

Hope it helps.

Thanks
Larry
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