matplotlib-users Mailing List for matplotlib

On 2/9/12 10:49 AM, Jeff Whitaker wrote:
> On 2/9/12 9:05 AM, Andreas H. wrote:
>> Hi,
>>
>> I'm trying to use pcolor on a masked array. I would like masked elements
>> to show up in a special color. I have written some code, but it does not
>> seem to work:
>>
>> I would appreciate any help :)
>>
>> Cheers,
>> Andreas.
>>
>> ---8<-------
>>
>> import matplotlib as mpl
>> import matplotlib.pyplot as plt
>>
>> from numpy import linspace
>> from numpy.random import randn
>> from numpy.ma import masked_invalid
>>
>> D = randn(12*72).reshape((12,72))
>> D[4,:] = nan
>> D[6,6] = nan
>>
>> D = masked_invalid(D)
>>
>> cmap = mpl.cm.bwr
>> cmap.set_bad('k', 1.)
>>
>> xbin = linspace(0, 12, 13)
>> ybin = linspace(-90, 90, 73)
>>
>> fig = plt.figure()
>> spl = fig.add_subplot(111)
>> pl = spl.pcolor(xbin, ybin, D.T, cmap=cmap, edgecolors='none',
>> vmin=-5, vmax=5)
> Andreas: That's because pcolor only fills polygons that are not masked
> - it does do anything with the masked ones.
>
> From the docstring:
>
> *X*, *Y* and *C* may be masked arrays. If either C[i, j], or one
> of the vertices surrounding C[i,j] (*X* or *Y* at [i, j], [i+1, j],
> [i, j+1],[i+1, j+1]) is masked, *]nothing is plotted.
>
> I suppose pcolor could be modified to fill the masked polygons with the
> color indicated by cmap.set_bad - I think that's what most people would
> expect.
>
> -Jeff
>
>
BTW: pcolormesh will do what you want.
-Jeff
-- 
Jeffrey S. Whitaker Phone : (303)497-6313
Meteorologist FAX : (303)497-6449
NOAA/OAR/PSD R/PSD1 Email : Jef...@no...
325 Broadway Office : Skaggs Research Cntr 1D-113
Boulder, CO, USA 80303-3328 Web : http://tinyurl.com/5telg

Paul Ivanov wrote:
> 
> Hi Phil,
> 
> phils, on 2012年02月04日 07:41, wrote:
>> Newbie to using matplotlib
> 
> welcome to the party :)
> 
>> Is it possible to use wx and have a window with say 2 buttons on where
>> when
>> clicking on either button a different graph will appear using a different
>> data set. Any examples?
> 
> Yes, it's possible. Here's a modified version of
> examples/event_handling/keypress_demo.py which toggles between
> two different axes when you press the 'w' key on your keyboard:
> one has green points connected by dashed lines, the other with
> multi-colored multi-sized scatter data.
> --------
> import numpy as np
> import matplotlib.pyplot as plt
> 
> plt.close('all')
> def press(event):
> print('press', event.key)
> if event.key=='w':
> visible = ax.get_visible()
> ax.set_visible(not visible)
> ax2.set_visible(visible)
> fig.canvas.draw()
> 
> fig = plt.figure()
> ax = fig.add_axes([.1,.1,.8,.8], label='one')
> ax2 = fig.add_axes([.1,.1,.8,.8], label='two')
> ax2.set_visible(False)
> 
> fig.canvas.mpl_connect('key_press_event', press)
> 
> ax.plot(np.random.rand(12), np.random.rand(12), 'go--')
> ax2.scatter(100*np.random.rand(12), 100*np.random.rand(12),
> c=np.random.rand(12), s=np.random.rand(12)*100)
> 
> plt.show()
> --------
> 
> I don't want to take away all of your fun, so have a look at
> adding (mouse clickable) buttons to this using either
> examples/widgets/buttons.py or examples/widgets/radio_buttons.py
> - depending on your preference.
> 
> best,
> -- 
> Paul Ivanov
> 314 address only used for lists, off-list direct email at:
> http://pirsquared.org | GPG/PGP key id: 0x0F3E28F7 
> 
> ------------------------------------------------------------------------------
> Keep Your Developer Skills Current with LearnDevNow!
> The most comprehensive online learning library for Microsoft developers
> is just 99ドル.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3,
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> 
> 
Paul
Thanks for this - really good. 
Day job is Crystal Reports developer and look foward to getting to use
Matplotlib.
Thanks again.
-- 
View this message in context: http://old.nabble.com/Switch-graphs-tp33263048p33296436.html
Sent from the matplotlib - users mailing list archive at Nabble.com.

Paul Ivanov wrote:
> 
> Hi Phil,
> 
> phils, on 2012年02月04日 07:41, wrote:
>> Newbie to using matplotlib
> 
> welcome to the party :)
> 
>> Is it possible to use wx and have a window with say 2 buttons on where
>> when
>> clicking on either button a different graph will appear using a different
>> data set. Any examples?
> 
> Yes, it's possible. Here's a modified version of
> examples/event_handling/keypress_demo.py which toggles between
> two different axes when you press the 'w' key on your keyboard:
> one has green points connected by dashed lines, the other with
> multi-colored multi-sized scatter data.
> --------
> import numpy as np
> import matplotlib.pyplot as plt
> 
> plt.close('all')
> def press(event):
> print('press', event.key)
> if event.key=='w':
> visible = ax.get_visible()
> ax.set_visible(not visible)
> ax2.set_visible(visible)
> fig.canvas.draw()
> 
> fig = plt.figure()
> ax = fig.add_axes([.1,.1,.8,.8], label='one')
> ax2 = fig.add_axes([.1,.1,.8,.8], label='two')
> ax2.set_visible(False)
> 
> fig.canvas.mpl_connect('key_press_event', press)
> 
> ax.plot(np.random.rand(12), np.random.rand(12), 'go--')
> ax2.scatter(100*np.random.rand(12), 100*np.random.rand(12),
> c=np.random.rand(12), s=np.random.rand(12)*100)
> 
> plt.show()
> --------
> 
> I don't want to take away all of your fun, so have a look at
> adding (mouse clickable) buttons to this using either
> examples/widgets/buttons.py or examples/widgets/radio_buttons.py
> - depending on your preference.
> 
> best,
> -- 
> Paul Ivanov
> 314 address only used for lists, off-list direct email at:
> http://pirsquared.org | GPG/PGP key id: 0x0F3E28F7 
> 
> ------------------------------------------------------------------------------
> Keep Your Developer Skills Current with LearnDevNow!
> The most comprehensive online learning library for Microsoft developers
> is just 99ドル.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3,
> Metro Style Apps, more. Free future releases when you subscribe now!
> http://p.sf.net/sfu/learndevnow-d2d
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
> 
> 
Paul
Thanks for this - really good. 
Day job is Crystal Reports developer and look foward to getting to use
Matplotlib.
Thanks again.
-- 
View this message in context: http://old.nabble.com/Switch-graphs-tp33263048p33296437.html
Sent from the matplotlib - users mailing list archive at Nabble.com.

Paul Ivanov wrote:
> 
> Hi Phil,
> 
> phils, on 2012年02月04日 07:41, wrote:
>> Newbie to using matplotlib
> 
> welcome to the party :)
> 
>> Is it possible to use wx and have a window with say 2 buttons on where
>> when
>> clicking on either button a different graph will appear using a different
>> data set. Any examples?
> 
> Yes, it's possible. Here's a modified version of
> examples/event_handling/keypress_demo.py which toggles between
> two different axes when you press the 'w' key on your keyboard:
> one has green points connected by dashed lines, the other with
> multi-colored multi-sized scatter data.
> --------
> import numpy as np
> import matplotlib.pyplot as plt
> 
> plt.close('all')
> def press(event):
> print('press', event.key)
> if event.key=='w':
> visible = ax.get_visible()
> ax.set_visible(not visible)
> ax2.set_visible(visible)
> fig.canvas.draw()
> 
> fig = plt.figure()
> ax = fig.add_axes([.1,.1,.8,.8], label='one')
> ax2 = fig.add_axes([.1,.1,.8,.8], label='two')
> ax2.set_visible(False)
> 
> fig.canvas.mpl_connect('key_press_event', press)
> 
> ax.plot(np.random.rand(12), np.random.rand(12), 'go--')
> ax2.scatter(100*np.random.rand(12), 100*np.random.rand(12),
> c=np.random.rand(12), s=np.random.rand(12)*100)
> 
> plt.show()
> --------
> 
> I don't want to take away all of your fun, so have a look at
> adding (mouse clickable) buttons to this using either
> examples/widgets/buttons.py or examples/widgets/radio_buttons.py
> - depending on your preference.
> 
> best,
> -- 
> Paul Ivanov
> 314 address only used for lists, off-list direct email at:
> http://pirsquared.org | GPG/PGP key id: 0x0F3E28F7 
> 
> ------------------------------------------------------------------------------
> Keep Your Developer Skills Current with LearnDevNow!
> The most comprehensive online learning library for Microsoft developers
> is just 99ドル.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3,
> Metro Style Apps, more. Free future releases when you subscribe now!
> http://p.sf.net/sfu/learndevnow-d2d
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
> 
> 
Paul
Thanks for this - really good. 
Day job is Crystal Reports developer and look foward to getting to use
Matplotlib.
Thanks again.
-- 
View this message in context: http://old.nabble.com/Switch-graphs-tp33263048p33296435.html
Sent from the matplotlib - users mailing list archive at Nabble.com.

Jae-Joon's code, make_axes_area_auto_adjustable has been a great help to
dynamically resizing my plots' axes area--such an improvement. But there
are two bugs I've noticed that I wonder if has been identified/fixed yet:
1) When I point-pick on the plot, the plot area still "jumps" (expands
vertically a small amount). It used to do this each time I point-picked,
but after upgrading MPL it now just does it the *first* time only. But is
it possible it can be fixed so it doesn't jump at all?
2) I just noticed that if a plot is resized so that the window that the
plot is embedded in is *narrower than the title on the plot*, the resizing
of the axes area gets very messed up (it gets *much8 narrower than is
necessary to fit the available area). I'm not sure what the best approach
to fixing this is, since it's not ideal to have a title not fit the
figure's area, either...is it possible to flow-wrap a plot title?
Thanks,
Che

On 2/9/12 9:05 AM, Andreas H. wrote:
> Hi,
>
> I'm trying to use pcolor on a masked array. I would like masked elements
> to show up in a special color. I have written some code, but it does not
> seem to work:
>
> I would appreciate any help :)
>
> Cheers,
> Andreas.
>
> ---8<-------
>
> import matplotlib as mpl
> import matplotlib.pyplot as plt
>
> from numpy import linspace
> from numpy.random import randn
> from numpy.ma import masked_invalid
>
> D = randn(12*72).reshape((12,72))
> D[4,:] = nan
> D[6,6] = nan
>
> D = masked_invalid(D)
>
> cmap = mpl.cm.bwr
> cmap.set_bad('k', 1.)
>
> xbin = linspace(0, 12, 13)
> ybin = linspace(-90, 90, 73)
>
> fig = plt.figure()
> spl = fig.add_subplot(111)
> pl = spl.pcolor(xbin, ybin, D.T, cmap=cmap, edgecolors='none',
> vmin=-5, vmax=5)
Andreas: That's because pcolor only fills polygons that are not masked 
- it does do anything with the masked ones.
 From the docstring:
*X*, *Y* and *C* may be masked arrays. If either C[i, j], or one
 of the vertices surrounding C[i,j] (*X* or *Y* at [i, j], [i+1, j],
 [i, j+1],[i+1, j+1]) is masked, *]nothing is plotted.
I suppose pcolor could be modified to fill the masked polygons with the 
color indicated by cmap.set_bad - I think that's what most people would 
expect.
-Jeff
-- 
Jeffrey S. Whitaker Phone : (303)497-6313
Meteorologist FAX : (303)497-6449
NOAA/OAR/PSD R/PSD1 Email : Jef...@no...
325 Broadway Office : Skaggs Research Cntr 1D-113
Boulder, CO, USA 80303-3328 Web : http://tinyurl.com/5telg

Hi,
I'm trying to use pcolor on a masked array. I would like masked elements
to show up in a special color. I have written some code, but it does not
seem to work:
I would appreciate any help :)
Cheers,
Andreas.
---8<-------
import matplotlib as mpl
import matplotlib.pyplot as plt
from numpy import linspace
from numpy.random import randn
from numpy.ma import masked_invalid
D = randn(12*72).reshape((12,72))
D[4,:] = nan
D[6,6] = nan
D = masked_invalid(D)
cmap = mpl.cm.bwr
cmap.set_bad('k', 1.)
xbin = linspace(0, 12, 13)
ybin = linspace(-90, 90, 73)
fig = plt.figure()
spl = fig.add_subplot(111)
pl = spl.pcolor(xbin, ybin, D.T, cmap=cmap, edgecolors='none',
 vmin=-5, vmax=5)

Hi,
I am trying to relabel the x-axis on a plot. I want it to have 10 evenly 
spaced labels ranging from 274 at zero to 283 at one increment short of 
the axis. My code is as follows:
 im.axes.xaxis.set_major_locator(py.MaxNLocator(10))
 im.axes.xaxis.set_ticklabels(range(274,284))
My understanding is that MaxNLocator defines the number of spaces 
between labels. I've tried a few variations on the above but can only 
seem to get the last label to be 282 or 284. Anyone know what I am doing 
wrong.
Thanks
D

Christopher Ellison :
> Taking the image size to (30,30) made all the segments appear, but their
> thickness was still not uniform. Using some sort of smoothing helped,
> but it still not displaying what the matrix was specified as: a set of
> blocks, somewhat resembling a line, all of which are the same color and
> thickness.
>
> Can I have matplotlib show the matrix as I have specified it? Or is
> that too naive (on my part)?
Thickness is not uniform, since the system MUST truncate something when 
you code your drawing as you do.
With sinc or bilinear interpolation you will see non-uniform shades of gray.
Bicubic interpolation will be - probably - much better.
But if you want to see your matrix as you want to see it, don't use 
imshow. Use figimage.
plt.figure(figsize=(7.5,7.5))
plt.figimage(x,cmap=plt.cm.gray_r)
And, for goodness sake... Don't shoot yourself in the foot by savefig, 
which stores not the matrix, but the figure, the drawing
of it after all the calamities. Use
plt.imsave('bug.png',x,cmap=plt.cm.gray_r)
Good luck.
Jerzy Karczmarczuk

Jerzy Karczmarczuk wrote the following on 02/08/2012 05:55 PM:
>
>> I am experiencing missing "segments" in the output of imshow()....
>>
>> Here is a minimal example:
>>
>> I have attached an example of the output. In theory, there should be
>> a continuous line from the left side of the picture to the right side.
>> The problem seems to occur across backends. Additionally, the
>> thickness of the segments is not uniform. Some are thinner than the
>> rest. Decreasing the value of N seems to make the issue go away.
>> Increasing the value of N makes the problem worse.
>>
>> Any ideas on what is going on and how I can fix it?
>>
> Imshow scales your geometry according to the figure size, and if you
> *insist* on having the "nearest" interpolation, you may lose pixels
> while drawing, it is as simple as that. No miracles.
>
> How to fix it?
> 1. Use bilinear, or sinc, or any smooth interpolation.
> 2. Make your figure big enough, say plt.figure(figsize=(14,14)).
>
Taking the image size to (30,30) made all the segments appear, but their 
thickness was still not uniform. Using some sort of smoothing helped, 
but it still not displaying what the matrix was specified as: a set of 
blocks, somewhat resembling a line, all of which are the same color and 
thickness.
Can I have matplotlib show the matrix as I have specified it? Or is 
that too naive (on my part)?

On Wednesday, February 8, 2012, Jerzy Karczmarczuk <
jer...@un...> wrote:
>
>> I am experiencing missing "segments" in the output of imshow()....
>>
>> Here is a minimal example:
>>
>> I have attached an example of the output. In theory, there should be
>> a continuous line from the left side of the picture to the right side.
>> The problem seems to occur across backends. Additionally, the
>> thickness of the segments is not uniform. Some are thinner than the
>> rest. Decreasing the value of N seems to make the issue go away.
>> Increasing the value of N makes the problem worse.
>>
>> Any ideas on what is going on and how I can fix it?
>>
> Imshow scales your geometry according to the figure size, and if you
> *insist* on having the "nearest" interpolation, you may lose pixels
> while drawing, it is as simple as that. No miracles.
>
> How to fix it?
> 1. Use bilinear, or sinc, or any smooth interpolation.
> 2. Make your figure big enough, say plt.figure(figsize=(14,14)).
>
> Jerzy Karczmarczuk
>
>
Agreed.
Your example above is basically the equivalent of rasterizing a line
(without anti-aliasing) and then down-scaling and possibly causing some
stretching due to changes in aspect ratio.
Because imshow() is unaware the you are actually drawing a line, the
backends can not take advantage of their "bag-o-tricks" to make it look
good.
Perhaps the example you provided was an oversimplified version of the
problem you are having?
Cheers!
Ben Root

> I am experiencing missing "segments" in the output of imshow()....
>
> Here is a minimal example:
>
> I have attached an example of the output. In theory, there should be 
> a continuous line from the left side of the picture to the right side. 
> The problem seems to occur across backends. Additionally, the 
> thickness of the segments is not uniform. Some are thinner than the 
> rest. Decreasing the value of N seems to make the issue go away. 
> Increasing the value of N makes the problem worse.
>
> Any ideas on what is going on and how I can fix it?
>
Imshow scales your geometry according to the figure size, and if you 
*insist* on having the "nearest" interpolation, you may lose pixels 
while drawing, it is as simple as that. No miracles.
How to fix it?
1. Use bilinear, or sinc, or any smooth interpolation.
2. Make your figure big enough, say plt.figure(figsize=(14,14)).
Jerzy Karczmarczuk