trouble reversing x-axis in octave

[Andy Boden]

Dear All,

I am having trouble reversing the x-axis (i.e. displaying from a larger
to a smaller value going left to right) on a plot generated by octave,
and I'm wondering if anyone has either seen this same symptom or know
what I am doing wrong.

Context dump:

I have developed an octave application that models astronomical
photometry with template spectral energy distributions (SEDs).

I would like to produce a plot with two horizontal axes -- spectral
wavelength on one horizontal axis (x2), and frequency on the other
horizontal (x1) axis.  Of course, these two quantities are inversely
related, so if one ascends left to right, the other must descend left to
right.

I am running octave 2.1.71 (via RPM package), and gnuplot 4.0.0 on a
Fedora Core 4 machine.

---

Symptomology:

I try to do the right thing in terms of setting the ranges for the two
axes (code extract):

  ## lMin & lMax in um
  eval(sprintf('__gnuplot_set__ x2range [%f:%f]',lMin,lMax));
  nuMin = cMKS / (lMin * 1e-6);
  nuMax = cMKS / (lMax * 1e-6);
  eval(sprintf('__gnuplot_set__ xrange [%f:%f]',nuMin,nuMax));

  __gnuplot_show__ x2range
  __gnuplot_show__ xrange

Output from the show commands above suggest that all is as it should be:


>      set x2range [ 0.115000 : 2.50000 ] noreverse nowriteback


>      set xrange [ 2.60522e+17 : 1.19840e+16 ] reverse nowriteback


Plots generated with the following command (more code): 

  __gnuplot_plot__ data using 1:2:5:3 t 'Input Photometry' axes x2y1 with 
xyerrorbars, \
        data using 1:4 t 'Model Photometry' axes x2y1 with points, \
        modelSED using 1:2 t 'Model Net (Source + Trans) SED' axes x2y1 with 
lines;



have BOTH wavelength and frequency increasing to the right (bummer!).
[I don't know really how to show that in this context; I don't think I
should attach a PostScript file to this message, so if anyone wants to
see the resulting plot I can send them a copy directly.]

Is it obvious to anyone what I am doing wrong, or is it possible I've
stumbled onto a bug in octave/gnuplot interaction?

Thanks in advance for your time in this matter.

- Andy


-- 
Andy Boden                               address@hidden
Michelson Science Center/Caltech         http://msc.caltech.edu
770 S. Wilson Ave, MS 100-22             626/395-1819
Pasadena, CA  91125                      



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