Problems with imshow logarithmic plot

Hello,

I'm trying to get imshow to plot logarithmic data. I'm having some problems
with the colorbar or data??

Note, I plot the max_dat value on the bottom of the figure, but it does not
seem to correspond with the values in the plot??? Any ideas? Also, does
anyone have some recommendations on how to better smooth the values, i.e.
make the plume less 'grainy'? Thanks!

My code is here:
http://numpy.pastebin.com/m4ae6331a

Example output is here:
http://picasaweb.google.com/washakie/Temp#5260746894103850338

···

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imshow doesn't handle logarithmic data. You'll want to use pcolor or pcolormesh instead.

As for the graininess, unfortunately, pcolor and pcolormesh don't support any kind of interpolation. (imshow does, but it can only draw uniform data).

Mike

John [H2O] wrote:

···

Hello,

I'm trying to get imshow to plot logarithmic data. I'm having some problems
with the colorbar or data??

Note, I plot the max_dat value on the bottom of the figure, but it does not
seem to correspond with the values in the plot??? Any ideas? Also, does
anyone have some recommendations on how to better smooth the values, i.e.
make the plume less 'grainy'? Thanks!

My code is here:
http://numpy.pastebin.com/m4ae6331a

Example output is here:
http://picasaweb.google.com/washakie/Temp#5260746894103850338

--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

Okay,

I can't find where I came up with the original solution to use imshow with
custom clevs... I think it was a thread on this forum possibly, or in an
example. But the point is that I recall there was some development talk
about improving the handling of log data for this issue.... Does anyone have
some pointers on these changes?

I guess what you would suggest is that I interpolate the data, then use
pcolor to plot it? Thanks.

Michael Droettboom-3 wrote:

···

imshow doesn't handle logarithmic data. You'll want to use pcolor or
pcolormesh instead.

As for the graininess, unfortunately, pcolor and pcolormesh don't
support any kind of interpolation. (imshow does, but it can only draw
uniform data).

Mike

John [H2O] wrote:

Hello,

I'm trying to get imshow to plot logarithmic data. I'm having some
problems
with the colorbar or data??

Note, I plot the max_dat value on the bottom of the figure, but it does
not
seem to correspond with the values in the plot??? Any ideas? Also, does
anyone have some recommendations on how to better smooth the values, i.e.
make the plume less 'grainy'? Thanks!

My code is here:
http://numpy.pastebin.com/m4ae6331a

Example output is here:
http://picasaweb.google.com/washakie/Temp#5260746894103850338

--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

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I should add here also, this doesn't explain for me why the values are
different?? Thoughts on that mtter?

Thanks!!

···

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The image is being plot in linear scale, while the scatter point is being plotted with log scale...?

John [H2O] wrote:

···

I should add here also, this doesn't explain for me why the values are
different?? Thoughts on that mtter?

Thanks!!

--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

Well, the image is being plotted using:
## create logorithmic scale
range_max = int(pl.ceil(dat_max))
step = int(pl.ceil(range_max/10))
logspace = 10.**np.linspace(-1, 4.0, 20) # 50 equally-spaced-in-log points
between 1.e-01 and 1.0e03
#plot#
im =
m.imshow(topodat,cmap=cm.s3pcpn,interpolation='nearest',vmin=dat_min,vmax=dat_max+(0.1*(dat_min-dat_max)))

The it is the 'Data Max' text that is of concern. Notice it does not equal
the max color according to the scale... the scatter point itself is not of
issue.

-john

Michael Droettboom-3 wrote:

···

The image is being plot in linear scale, while the scatter point is
being plotted with log scale...?

John [H2O] wrote:

I should add here also, this doesn't explain for me why the values are
different?? Thoughts on that mtter?

Thanks!!

--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's
challenge
Build the coolest Linux based applications with Moblin SDK & win great
prizes
Grand prize is a trip for two to an Open Source event anywhere in the
world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
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