[Matplotlib-users] Request for feature: negative to positive log-axis

[Arnold M. <arn...@wu...>]

Dear all,

Perhaps this idea appears strange to some, but in my field (atmospheric
turbulence) it is a common problem: I want to plot data with a log-axis (say
the x-axis) with both positive and negative numbers for x. This implies that I
want to zoom in on small values of |x|. The way to do this, is to define a
'gap' around zero in which no data exist, or are ignored. So if my x-data would
range
from -10 to -0.01 and from 0.01 to 10, the x-axis would look like:

|-------|-------|-------|-------|-------|------|
-10     -1     -0.1  +/-0.01   0.1      1      10

There are few (if any) plotting programs that can do this, but it would make
life a lot easier for me. By now I have hacked my own pylab script to do this,
but it has many limitations. To do it properly, it should be done on a somewhat
lower level in the code, I suppose. The idea is to split the data into either 2
(semilogx and semilogy) or 4 quadrants (loglog) and to plot the data in each
quadrant seperately. If the lower limit of the x-axis (or y-axis) is taken
positive, a normal semilogx (or semilogy) plot is recovered.

More people that need/like this? Any volunteers who know what they are doing (in
terms of low-level pylab coding)?

Regards,

Arnold

-- 
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Arnold F. Moene                          NEW tel: +31 (0)317 482604
Meteorology and Air Quality Group            fax: +31 (0)317 482811
Wageningen University                   e-mail: Arnold.Moene at wur.nl
Duivendaal 2                             url: http://www.met.wau.nl
6701 AP  Wageningen
The Netherlands
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