matplotlib-users Mailing List for matplotlib

On 2014/06/17, 8:59 AM, Bruno Pace wrote:
> Hi all,
>
> I'm trying to use imshow to plot some values which fall on the interval
> [0,1]. I need to
> use a logscale to emphasize the scales of the data. The solution I found
> checking some discussions was like this
>
> plt.imshow(X, interpolation='none', norm=matplotlib.colors.LogNorm())
>
> However, I notice that the way these colors are assigned are not always
> the same (although my data always contains the minimum value 0.0 and
>   the maximum 1.0). I need to have a coherent color scale to indicate
> the real values. Is it easier to do the color code myself? What is the
> proper way of tackling this problem??

Use the vmin and vmax kwargs to LogNorm, remembering that vmin must be 
greater than zero for a log scale.

Eric

>
> It's pretty much the same problem described here, but with a logscale...
>
> http://stackoverflow.com/questions/7875688/how-can-i-create-a-standard-colorbar-for-a-series-of-plots-in-python
>
>
> Thank you very much!
>
> Bruno
>
>
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Hi all,

I'm trying to use imshow to plot some values which fall on the interval
[0,1]. I need to
use a logscale to emphasize the scales of the data. The solution I found
checking some discussions was like this

plt.imshow(X, interpolation='none', norm=matplotlib.colors.LogNorm())

However, I notice that the way these colors are assigned are not always the
same (although my data always contains the minimum value 0.0 and  the
maximum 1.0). I need to have a coherent color scale to indicate the real
values. Is it easier to do the color code myself? What is the proper way of
tackling this problem??

It's pretty much the same problem described here, but with a logscale...

http://stackoverflow.com/questions/7875688/how-can-i-create-a-standard-colorbar-for-a-series-of-plots-in-python


Thank you very much!

Bruno

Based on the example you posted, you need like:

import matplotlib.pyplot as plt
fig, ax = plt.subplots()
ax.contour(data)
ax.axhline(magic_value)


On Mon, Jun 16, 2014 at 1:30 AM, dydy2014 <dya...@gm...> wrote:

> Hello all,
>
> I have contour plot like this and I have problem to pick a particular data
> along red line and save it.
> How do I make it with python program?
>
> <http://matplotlib.1069221.n5.nabble.com/file/n43532/190311.png>
>
> Thank you in advance.
>
> Dydy
>
>
>
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>
>
> ------------------------------------------------------------------------------
> HPCC Systems Open Source Big Data Platform from LexisNexis Risk Solutions
> Find What Matters Most in Your Big Data with HPCC Systems
> Open Source. Fast. Scalable. Simple. Ideal for Dirty Data.
> Leverages Graph Analysis for Fast Processing & Easy Data Exploration
> http://p.sf.net/sfu/hpccsystems
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> Matplotlib-users mailing list
> Mat...@li...
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>

Perfect, many thanks!

So the trick was _not_ to do "show()" in A.py

(Moreover, doing "draw()" in A.py also seems necessary... even though I
don't really get why -- actually in my own more complicated program, it
works also without this draw...)



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