matplotlib-users Mailing List for matplotlib

Great, matshow() works for my requirements.
Although, I must comment that its placement of tickbars seems 
inappropriate for a matrix visualisation. For example, for the following 
simple example:
import pylab
matrix = pylab.array([[1,2,3],[4,5,6],[1,1,4]])
pylab.matshow(matrix, cmap=pylab.cm.gray)
pylab.show()
tick marks and labels are produced for [0.5,1.5,2.5] in addition to the 
appropriate integral ones. It's obviously not an issue for larger 
matrices.
Further, I would think a setting like align='center' in pylab.bar() would 
be appropriate. Any simple way of doing this without manually setting the 
ticks and labels (ironically using forced *.5 ticks)?
I guess I should code and submit it myself. :)
Thanks very much,
Suresh
On Thu, 1 Mar 2007, Eric Firing wrote:
> Suresh Pillai wrote:
>> I am using imshow to visualise matrices. When I use align='upper'
>> (default), the origin is still displayed in the lower left corner on the
>> axes - i.e. the y-axis is wrong. The data is plotted correctly with the
>> origin in the upper left corner.
>>
>> Seems to be a bug?
>
> No, this is just the way it was designed and has always been. You can use 
> the "extent" kwarg to control the axes:
>
> * origin is either upper or lower, which indicates where the [0,0]
> index of the array is in the upper left or lower left corner of
> the axes. If None, default to rc image.origin
> * extent is a data xmin, xmax, ymin, ymax for making image plots
> registered with data plots. Default is the image dimensions
> in pixels
>
> See the code in axes.spy() for an example of how to get what you want using 
> imshow and the extent kwarg; or use pylab.matshow instead of pylab.imshow. 
> (Probably there should be an axes.matshow convenience method, with 
> pylab.matshow as a wrapper that autogenerates a figure if needed. But at the 
> moment there isn't.)
>
> Eric
>
>>
>> Cheers,
>> Suresh
>>
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>

Suresh Pillai wrote:
> I am using imshow to visualise matrices. When I use align='upper' 
> (default), the origin is still displayed in the lower left corner on the 
> axes - i.e. the y-axis is wrong. The data is plotted correctly with the 
> origin in the upper left corner.
> 
> Seems to be a bug?
No, this is just the way it was designed and has always been. You can 
use the "extent" kwarg to control the axes:
 * origin is either upper or lower, which indicates where the [0,0]
 index of the array is in the upper left or lower left corner of
 the axes. If None, default to rc image.origin
 * extent is a data xmin, xmax, ymin, ymax for making image plots
 registered with data plots. Default is the image dimensions
 in pixels
See the code in axes.spy() for an example of how to get what you want 
using imshow and the extent kwarg; or use pylab.matshow instead of 
pylab.imshow. (Probably there should be an axes.matshow convenience 
method, with pylab.matshow as a wrapper that autogenerates a figure if 
needed. But at the moment there isn't.)
Eric
> 
> Cheers,
> Suresh
> 
> -------------------------------------------------------------------------
> Take Surveys. Earn Cash. Influence the Future of IT
> Join SourceForge.net's Techsay panel and you'll get the chance to share your
> opinions on IT & business topics through brief surveys-and earn cash
> http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
> _______________________________________________
> Matplotlib-users mailing list
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I am using imshow to visualise matrices. When I use align='upper' 
(default), the origin is still displayed in the lower left corner on the 
axes - i.e. the y-axis is wrong. The data is plotted correctly with the 
origin in the upper left corner.
Seems to be a bug?
Cheers,
Suresh

I found an example on the web that illustrates the question I posted earlie=
r about axes. See:=0A=0Ahttp://www.scipy.org/Cookbook/Matplotlib/Multicolo=
redLine=0A=0ANotice that the y-axis goes from (-1.1, 1.1) but the first lab=
el is at -1.0. I really don't like that because when I read values off th=
e graph, I have to keep reminding myself that the origin is at -1.1. This=
 may seem trivial but if you have to think, walk, chew gums at the same tim=
e you're reading the graph, it gets annoying - particularly if you have to =
read lots of these graphs.=0A=0AIs there a way to force the label to start =
at -1.1 instead of -1.0?=0A=0AThanks,=0A =0A--=0AJohn Henry=0A=0A

Hello darkside,
I set up a little program hoping it offers a solution to your problem.
Matthias
>-------------------------------------------------------------------------------
from numpy.random import uniform 
import pylab 
Nt = 20
x,y = uniform(size=(100,Nt+1)),uniform(size=(100,Nt+1))
pylab.ion()
ax1 = pylab.subplot(211)
pylab.ylabel('Posiciones')
ax2 = pylab.subplot(212)
pylab.ylabel('Momentos')
line1,= ax1.plot(x[:,0], x[:,1])
line2,= ax2.plot(y[:,0], y[:,1])
pylab.draw()
pylab.draw()
# alternative you could use
"""
pylab.axes(ax1)
line1,= pylab.plot(x[:,0], x[:,1])
pylab.axes(ax2)
line2,= pylab.plot(y[:,0], y[:,1])
pylab.draw()
"""
for k in pylab.arange(Nt):
 line1.set_ydata(x[:,k+1])
 line2.set_ydata(y[:,k+1])
 pylab.draw()
 pylab.draw()
pylab.ioff()
pylab.show()
>-------------------------------------------------------------------