matplotlib-users Mailing List for matplotlib

 Stephen> Sounds like an interesting project. The first item I'd
 Stephen> have on a list of desired features is, surprise, the
 Stephen> ability to load multiple aligned images and blink between
 Stephen> them.
With the new keypress event handling in matplotlib-0.70, and the
cleanup to make sure the visible property is respected, this is pretty
easy. The example below is more complicated than you need for the
usual case, since it handles images of different pixel dimensions that
occupy the same physical dimensions, but it gives you the idea (btw,
this is now examples/toggle_images.py, which contains a bit more
information in the header)
What's the second item on the list :-)
JDH
from pylab import *
# two images x1 is initially visible, x2 is not
x1 = rand(100, 100)
x2 = rand(150, 175)
# arbitrary extent - both images must have same extent if you want
# them to be resampled into the same axes space
extent = (0,1,0,1) 
im1 = imshow(x1, extent=extent)
im2 = imshow(x2, extent=extent, hold=True)
im2.set_visible(False)
def toggle_images(event):
 'toggle the visible state of the two images'
 if event.key != 't': return
 b1 = im1.get_visible()
 b2 = im2.get_visible()
 im1.set_visible(not b1)
 im2.set_visible(not b2)
 draw()
connect('key_press_event', toggle_images)
#savefig('toggle_images')
show()

This is (hopefully) a final rollup of what is (should be) a fairly
stable tree. Mainly I wanted to send a release notification out to
the larger python community (scipy/numpy/python-list) since I haven't
done that since 0.60 (July 2004). 
For the major releases, I tend to try and shy away from new features
preferring a stable src. But for you hardened, grizzled matplotlib
veterans, there are a few enticements nonetheless
 - pie charts and new example/pie_demo.py. See
 http://matplotlib.sf.net/screenshots.html#pie_demo
 - support for object picking - see examples/picker_demo.py. As
 people test this out and we settle on an interface, this will
 probably become part of the core, as will other keypress
 functionality for navigation, grid toogle, zoom toggle etc.
 - Fixed coords notification in wx toolbar 
 - key press and release event supported across backends -- see
 examples/keypress_demo.py
 - added Shadow patch class to provide a shadow effect for polygons,
 legends, pie charts -
 http://matplotlib.sf.net/screenshots.html#legend_demo
 - new examples/text_rotation.py demonstrates how text rotations and
 alignment work in matplotlib. 
Bug fixes
 - Fixed PS mathtext bug where color was not set
 - Fixed an agg text rotation alignment bug, fixed some text kwarg
 processing bugs
 - Refactored event handling - multiple connects and disconnects now
 work across backends. See examples/coords_demo.py, especially
 with test_disconnect
 - Fixed a tkagg interactive bug that caused segfaults in some
 conditions.
As usual, downloads at http://sourceforge.net/projects/matplotlib
JDH

>>>>> "seberino" == seberino <seb...@sp...> writes:
 seberino> Normally x-axis (horizontal) values increase to right
 seberino> and y-axis (vertical) values increase up the page.
 seberino> Is it easy/possible to reverse this for the y-axis??
 seberino> (So that y-values **decrease** up the page for some
 seberino> range?)
 ylim(ymax, ymin)
OR
 xlim(xmax, xmin)
See, for example, http://matplotlib.sf.net/examples/invert_axes.py

>>>>> "Randy" == Randy Heiland <he...@in...> writes:
 Randy> Can matplotlib do image plots of a nonuniform mesh? from
 Randy> matplotlib.matlab import *
 Randy> x=array([0.,0.5,0.51,4.]) y=array([0.,1.]) X,Y =
 Randy> meshgrid(x,y) Z=array([[0,1,1,2],[0,1,1,2]]) im =
 Randy> imshow(Z,cmap=cm.jet) show()
Yes, but note that the pcolor has numrows-1 rows and numcols-1 cols
since the endpoints must be specified in your X,Y arrays
 x = array([0.,0.5,0.6,4.])
 y = array([0.,1.,4])
 X,Y = meshgrid(x,y)
 Z = array([[0,1,2,2],[0,1,1,2],[2,0,1,2]])
 pcolor(X, Y, Z, cmap=cm.jet)
JDH

Can matplotlib do image plots of a nonuniform mesh?
from matplotlib.matlab import *
x=array([0.,0.5,0.51,4.])
y=array([0.,1.])
X,Y = meshgrid(x,y)
Z=array([[0,1,1,2],[0,1,1,2]])
im = imshow(Z,cmap=cm.jet)
show()
thanks, Randy

Normally x-axis (horizontal) values increase to right
and y-axis (vertical) values increase up the page.
Is it easy/possible to reverse this for the y-axis??
(So that y-values **decrease** up the page for some range?)
Chris
--
_______________________________________
Christian Seberino, Ph.D.
SPAWAR Systems Center San Diego
Code 2872
49258 Mills Street, Room 158
San Diego, CA 92152-5385
U.S.A.
Phone: (619) 553-9973
Fax : (619) 553-6521
Email: seb...@sp...
_______________________________________

>>>>> "seberino" == seberino <seb...@sp...> writes:
 seberino> It seems if your grid has 20 rows ( different y values)
 seberino> of points that you won't get 20 colored horizontal
 seberino> strips but rather *19*. This is because we must lose
 seberino> one row to specify the top and/or bottom EDGE of the
 seberino> plot.... so XX rows means (XX-1) rows of colored
 seberino> squares.
yep that's right, a frequent source of confusion. 
 seberino> Please tell me if this is right but more importantly,
 seberino> how to most wisely remove the white horizontal strip
 seberino> from this pcolor plot.
Well it would help if you posted your code, but my guess is that you
need to set your axis limits to equal your ymin/ymax of the pcolor.
Perhaps this example will give you a hint
 >>> pcolor(rand(10,7)) # no white strip...
 >>> ylim(0,11) # a white strip because the ylim is wrong
In essence, the axis autoscaler will round up, eg 4990 to 5000, to
make nice integer ticks. With pcolors and images, you often don't
want this, so use the axis, xlim, and/or ylim commands to set the
limits properly.
Eg
 ymin = min(ravel(Y))
 ymax = max(ravel(Y))
 ylim(ymin, ymax)
Also, if your x and y grids are equally spaced, you'll get much better
performance for large arrays, as well as more interpolation options,
if you use imshow with the extent kwarg to set the extent of your
image data.
JDH

I'm getting great pcolor plots like attached one and learning lots
about it. So far so good. One minor question if you don't mind...
I'm getting an empty white strip across the top of attached plot
as you can see which led me deeper into workings of pcolor function.
It seems if your grid has 20 rows ( different y values) of points
that you won't get 20 colored horizontal strips but rather
*19*. This is because we must lose one row to specify the top
and/or bottom EDGE of the plot.... so XX rows means (XX-1) rows
of colored squares.
Please tell me if this is right but more importantly, how to
most wisely remove the white horizontal strip from this
pcolor plot.
Thanks!
chris