matplotlib-users Mailing List for matplotlib

Thanks for the report, Ethan,

Ethan Swint, on 2012-01-10 16:34,  wrote:
> Can anyone else reproduce?

Confirming, this is a bug. We need to change the matplotlib code,
but I'm not sure how to proceed. I've filed it as the ominously
numbered matplotlib issue #666

https://github.com/matplotlib/matplotlib/issues/666

> It seems that 'xi,yi = np.meshgrid(xi,yi)' from line 2766 of mlab.py 
> doesn't always produce uniformly spaced data, as the test for uniform 
> data fails at line 2779.  Ignoring the error, however, results in 
> satisfactory evaluation of interp() on 2783.

That's not quite the issue here, as meshgrid simply reshapes and
repeats the data that you hand it. 

At first I was going to blame linspace, because a similar issue
came up on this list late last year, and in that example, simply
using arange instead of linspace resolved the issue:

http://old.nabble.com/constant-spacing-with-griddata-td33007330.html#a33007330

There, I considered the possibility that either (or both) the
numpy and mpl code should be changed. 

With your example, I'm convinced now the MPL code needs to
change, since here, linspace and arange produce identical
results. The reason I'm not sure how to proceed is that the
difference between dx.max() and dx.min() can be an order of
magnitude greater than the epsx value it is compared against.
Here's a modification to your example that does this

  In [155]: xi = np.linspace(0,603,100);dx =np.diff(xi); dx.ptp()
  Out[155]: 0.00000000000011368684
  
  In [157]: zi = griddata(x,y,z,xi,yi,interp='linear')
  --error--
  In [158]: debug
  > /home/pi/usr/local/lib/python2.6/site-packages/matplotlib/mlab.py(2780)griddata()
     2779             if dx.max()-dx.min() > epsx or
  dy.max()-dy.min() > epsy:
  -> 2780                 raise ValueError("output grid must have
  constant spacing"
     2781                                  " when using
  interp='linear'")
  
  ipdb> dx.ptp()
  1.1368683772161603e-13
  ipdb> epsx
  1.0000000000000001e-15
  ipdb> 

I believe that this has to do with the limited precision and
non-uniformity of the possible numbers represented by the
floating point standard. The check for constant spacing likely
should take into account and compare dx.ptp() to the average dx
itself, or something like that.

best,
-- 
Paul Ivanov
314 address only used for lists,  off-list direct email at:
http://pirsquared.org | GPG/PGP key id: 0x0F3E28F7 

Hi-

I was working off of the example listed at 
http://matplotlib.sourceforge.net/examples/pylab_examples/griddata_demo.html, 
adapting it to my own data, and encountered the following error on MLAB 
1.1.0, Python 2.7.2:
<code>

from numpy.random import uniform, seed
from matplotlib.mlab import griddata
import matplotlib.pyplot as plt
import numpy as np
# make up data.
#npts = int(raw_input('enter # of random points to plot:'))
seed(0)
npts = 200
x = uniform(-2,2,npts)
y = uniform(-2,2,npts)
z = x*np.exp(-x**2-y**2)
xi = np.linspace(0,60,100)  # <= my xdata range
yi = np.linspace(0,0.9,200) # <= my ydata range
zi = griddata(x,y,z,xi,yi,interp='linear')

</code>

which produces 
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
C:\Users\Ethan\code\PythonScripts\<ipython-input-7-51e10e494403> in 
<module>()
----> 1 zi = griddata(x,y,z,xi,yi,interp='linear')

It seems that 'xi,yi = np.meshgrid(xi,yi)' from line 2766 of mlab.py 
doesn't always produce uniformly spaced data, as the test for uniform 
data fails at line 2779.  Ignoring the error, however, results in 
satisfactory evaluation of interp() on 2783.

Can anyone else reproduce?

Regards,
Ethan

I am still seeing the error below in matplotlib-1.1.0 - the bug occurs
when the user installs our software to the directory "version1", uses
that installation, then installs "version2" and removes "version1",
which breaks matplotlib because (unlike any other Python module I've
ever used) the absolute font paths are hardwired into the user's local
configuration.  I was told nearly a year ago that this was already
fixed in SVN, but clearly this is not the case.  Is there a workaround
for this other than emailing every user who complains and telling
him/her to rm -rf ~/.matplotlib?

thanks,
Nat

 File "/Users/nat/version2/Python.framework/Versions/Current/lib/python2.7/site-packages/matplotlib/backends/backend_wxagg.py",
line 59, in draw
   FigureCanvasAgg.draw(self)
 File "/Users/nat/version2/Python.framework/Versions/Current/lib/python2.7/site-packages/matplotlib/backends/backend_agg.py",
line 401, in draw
   self.figure.draw(self.renderer)
 File "/Users/nat/version2/Python.framework/Versions/Current/lib/python2.7/site-packages/matplotlib/artist.py",
line 55, in draw_wrapper
   draw(artist, renderer, *args, **kwargs)
 File "/Users/nat/version2/Python.framework/Versions/Current/lib/python2.7/site-packages/matplotlib/figure.py",
line 884, in draw
   func(*args)
 File "/Users/nat/version2/Python.framework/Versions/Current/lib/python2.7/site-packages/matplotlib/artist.py",
line 55, in draw_wrapper
   draw(artist, renderer, *args, **kwargs)
 File "/Users/nat/version2/Python.framework/Versions/Current/lib/python2.7/site-packages/matplotlib/axes.py",
line 1983, in draw
   a.draw(renderer)
 File "/Users/nat/version2/Python.framework/Versions/Current/lib/python2.7/site-packages/matplotlib/artist.py",
line 55, in draw_wrapper
   draw(artist, renderer, *args, **kwargs)
 File "/Users/nat/version2/Python.framework/Versions/Current/lib/python2.7/site-packages/matplotlib/axis.py",
line 1037, in draw
   ticklabelBoxes, ticklabelBoxes2 =
self._get_tick_bboxes(ticks_to_draw, renderer)
 File "/Users/nat/version2/Python.framework/Versions/Current/lib/python2.7/site-packages/matplotlib/axis.py",
line 988, in _get_tick_bboxes
   extent = tick.label1.get_window_extent(renderer)
 File "/Users/nat/version2/Python.framework/Versions/Current/lib/python2.7/site-packages/matplotlib/text.py",
line 747, in get_window_extent
   bbox, info = self._get_layout(self._renderer)
 File "/Users/nat/version2/Python.framework/Versions/Current/lib/python2.7/site-packages/matplotlib/text.py",
line 300, in _get_layout
   ismath=False)
 File "/Users/nat/version2/Python.framework/Versions/Current/lib/python2.7/site-packages/matplotlib/backends/backend_agg.py",
line 183, in get_text_width_height_descent    font =
self._get_agg_font(prop)
 File "/Users/nat/version2/Python.framework/Versions/Current/lib/python2.7/site-packages/matplotlib/backends/backend_agg.py",
line 224, in _get_agg_font   font = FT2Font(str(fname))
RuntimeError: Could not open facefile
/Users/nat/version1/Python.framework/Versions/Current/lib/python2.7/site-packages/matplotlib/mpl-data/fonts/ttf/VeraMono.ttf;
Cannot_Open_Resource

Regardless of exactly which polynomial you are after, I've showed you how
to plot a cheb. poly.  Can you not work with the code given and plot the
exact variation of polynomial you want?



On Tue, Jan 10, 2012 at 9:46 AM, Fabien Lafont <laf...@gm...>wrote:

> No I just want to plot the third Shebitchev polynomial.
>
> 2012/1/10 Daniel Hyams <dh...@gm...>:
> > I think that you're misusing Chebyshev (do you really only want to give
> "3"
> > as a coefficient..which is just the constant function 3), and you have to
> > evaluate it in order to give matplotlib some x and y data to plot.
> >
> > from matplotlib import pyplot as plt
> > import numpy as np
> >
> > x = np.linspace(-1.0,1.0)
> > test = np.polynomial.Chebyshev((1,2,3))
> > y = test(x)
> > plt.plot(x,y)
> > plt.show()
> >
> >
> >
> > On Tue, Jan 10, 2012 at 9:10 AM, Fabien Lafont <laf...@gm...>
> > wrote:
> >>
> >> I'm trying to plot Chebyshev polynolmials using:
> >> numpy.polynomial.Chebyshev:
> >>
> >>
> >> import math
> >> from numpy import *
> >> from numpy import polynomial as pol
> >> from pylab import *
> >> from scipy import *
> >> from scipy import optimize
> >> import warnings
> >> warnings.simplefilter('ignore', np.RankWarning)
> >>
> >>
> >> test = pol.Chebyshev(3)
> >> print test
> >> plot (test)
> >>
> >>
> >> show()
> >> =======================================================================
> >>
> >> The print return:      cheb([ 3.])
> >>
> >> =======================================================================
> >> and plot :
> >>
> >>
> >> Traceback (most recent call last):
> >>  File "T:\Dropbox\Thèse\Python\fit sonde\test_poly_Tcheb.py", line
> >> 32, in <module>
> >>    plot (test)
> >>  File "C:\Python27\lib\site-packages\matplotlib\pyplot.py", line 2458,
> in
> >> plot
> >>    ret = ax.plot(*args, **kwargs)
> >>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 3849, in
> >> plot
> >>    self.add_line(line)
> >>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 1443,
> >> in add_line
> >>    self._update_line_limits(line)
> >>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 1451,
> >> in _update_line_limits
> >>    p = line.get_path()
> >>  File "C:\Python27\lib\site-packages\matplotlib\lines.py", line 644,
> >> in get_path
> >>    self.recache()
> >>  File "C:\Python27\lib\site-packages\matplotlib\lines.py", line 401, in
> >> recache
> >>    y = np.asarray(yconv, np.float_)
> >>  File "C:\Python27\lib\site-packages\numpy\core\numeric.py", line
> >> 235, in asarray
> >>    return array(a, dtype, copy=False, order=order)
> >> TypeError: float() argument must be a string or a number
> >>
> >>
> >>
> ------------------------------------------------------------------------------
> >> Write once. Port to many.
> >> Get the SDK and tools to simplify cross-platform app development. Create
> >> new or port existing apps to sell to consumers worldwide. Explore the
> >> Intel AppUpSM program developer opportunity.
> appdeveloper.intel.com/join
> >> http://p.sf.net/sfu/intel-appdev
> >> _______________________________________________
> >> Matplotlib-users mailing list
> >> Mat...@li...
> >> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
> >
> >
> >
> >
> > --
> > Daniel Hyams
> > dh...@gm...
> >
> >
> ------------------------------------------------------------------------------
> > Write once. Port to many.
> > Get the SDK and tools to simplify cross-platform app development. Create
> > new or port existing apps to sell to consumers worldwide. Explore the
> > Intel AppUpSM program developer opportunity. appdeveloper.intel.com/join
> > http://p.sf.net/sfu/intel-appdev
> > _______________________________________________
> > Matplotlib-users mailing list
> > Mat...@li...
> > https://lists.sourceforge.net/lists/listinfo/matplotlib-users
> >
>



-- 
Daniel Hyams
dh...@gm...

I'm not used to reply-all


---------- Forwarded message ----------
From:  <jos...@gm...>
Date: Tue, Jan 10, 2012 at 10:20 AM
Subject: Re: [Matplotlib-users] How to plot Chebyshev polynolmials
To: Fabien Lafont <laf...@gm...>


On Tue, Jan 10, 2012 at 9:46 AM, Fabien Lafont <laf...@gm...> wrote:
> No I just want to plot the third Shebitchev polynomial.

the vander functions give you the basis functions for a given x, or
use coefficients only for the polynomial you want, if I understand
correctly what you want

>>> import numpy as np
>>> from numpy import polynomial as poly
>>> chebs = [poly.Chebyshev(coef) for coef in np.eye(5)]
>>> for p in chebs: plt.plot(x, p(x))
...
[<matplotlib.lines.Line2D object at 0x046D91F0>]
[<matplotlib.lines.Line2D object at 0x046D9510>]
[<matplotlib.lines.Line2D object at 0x046D9830>]
[<matplotlib.lines.Line2D object at 0x046D9B50>]
[<matplotlib.lines.Line2D object at 0x046D9E70>]
>>> plt.show()

or
>>> plt.plot(poly.chebvander(x, 5))

Josef



>
> 2012/1/10 Daniel Hyams <dh...@gm...>:
>> I think that you're misusing Chebyshev (do you really only want to give "3"
>> as a coefficient..which is just the constant function 3), and you have to
>> evaluate it in order to give matplotlib some x and y data to plot.
>>
>> from matplotlib import pyplot as plt
>> import numpy as np
>>
>> x = np.linspace(-1.0,1.0)
>> test = np.polynomial.Chebyshev((1,2,3))
>> y = test(x)
>> plt.plot(x,y)
>> plt.show()
>>
>>
>>
>> On Tue, Jan 10, 2012 at 9:10 AM, Fabien Lafont <laf...@gm...>
>> wrote:
>>>
>>> I'm trying to plot Chebyshev polynolmials using:
>>> numpy.polynomial.Chebyshev:
>>>
>>>
>>> import math
>>> from numpy import *
>>> from numpy import polynomial as pol
>>> from pylab import *
>>> from scipy import *
>>> from scipy import optimize
>>> import warnings
>>> warnings.simplefilter('ignore', np.RankWarning)
>>>
>>>
>>> test = pol.Chebyshev(3)
>>> print test
>>> plot (test)
>>>
>>>
>>> show()
>>> =======================================================================
>>>
>>> The print return:      cheb([ 3.])
>>>
>>> =======================================================================
>>> and plot :
>>>
>>>
>>> Traceback (most recent call last):
>>>  File "T:\Dropbox\Thèse\Python\fit sonde\test_poly_Tcheb.py", line
>>> 32, in <module>
>>>    plot (test)
>>>  File "C:\Python27\lib\site-packages\matplotlib\pyplot.py", line 2458, in
>>> plot
>>>    ret = ax.plot(*args, **kwargs)
>>>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 3849, in
>>> plot
>>>    self.add_line(line)
>>>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 1443,
>>> in add_line
>>>    self._update_line_limits(line)
>>>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 1451,
>>> in _update_line_limits
>>>    p = line.get_path()
>>>  File "C:\Python27\lib\site-packages\matplotlib\lines.py", line 644,
>>> in get_path
>>>    self.recache()
>>>  File "C:\Python27\lib\site-packages\matplotlib\lines.py", line 401, in
>>> recache
>>>    y = np.asarray(yconv, np.float_)
>>>  File "C:\Python27\lib\site-packages\numpy\core\numeric.py", line
>>> 235, in asarray
>>>    return array(a, dtype, copy=False, order=order)
>>> TypeError: float() argument must be a string or a number
>>>
>>>
>>> ------------------------------------------------------------------------------
>>> Write once. Port to many.
>>> Get the SDK and tools to simplify cross-platform app development. Create
>>> new or port existing apps to sell to consumers worldwide. Explore the
>>> Intel AppUpSM program developer opportunity. appdeveloper.intel.com/join
>>> http://p.sf.net/sfu/intel-appdev
>>> _______________________________________________
>>> Matplotlib-users mailing list
>>> Mat...@li...
>>> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>>
>>
>>
>>
>> --
>> Daniel Hyams
>> dh...@gm...
>>
>> ------------------------------------------------------------------------------
>> Write once. Port to many.
>> Get the SDK and tools to simplify cross-platform app development. Create
>> new or port existing apps to sell to consumers worldwide. Explore the
>> Intel AppUpSM program developer opportunity. appdeveloper.intel.com/join
>> http://p.sf.net/sfu/intel-appdev
>> _______________________________________________
>> Matplotlib-users mailing list
>> Mat...@li...
>> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>>
>
> ------------------------------------------------------------------------------
> Write once. Port to many.
> Get the SDK and tools to simplify cross-platform app development. Create
> new or port existing apps to sell to consumers worldwide. Explore the
> Intel AppUpSM program developer opportunity. appdeveloper.intel.com/join
> http://p.sf.net/sfu/intel-appdev
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users

No I just want to plot the third Shebitchev polynomial.

2012/1/10 Daniel Hyams <dh...@gm...>:
> I think that you're misusing Chebyshev (do you really only want to give "3"
> as a coefficient..which is just the constant function 3), and you have to
> evaluate it in order to give matplotlib some x and y data to plot.
>
> from matplotlib import pyplot as plt
> import numpy as np
>
> x = np.linspace(-1.0,1.0)
> test = np.polynomial.Chebyshev((1,2,3))
> y = test(x)
> plt.plot(x,y)
> plt.show()
>
>
>
> On Tue, Jan 10, 2012 at 9:10 AM, Fabien Lafont <laf...@gm...>
> wrote:
>>
>> I'm trying to plot Chebyshev polynolmials using:
>> numpy.polynomial.Chebyshev:
>>
>>
>> import math
>> from numpy import *
>> from numpy import polynomial as pol
>> from pylab import *
>> from scipy import *
>> from scipy import optimize
>> import warnings
>> warnings.simplefilter('ignore', np.RankWarning)
>>
>>
>> test = pol.Chebyshev(3)
>> print test
>> plot (test)
>>
>>
>> show()
>> =======================================================================
>>
>> The print return:      cheb([ 3.])
>>
>> =======================================================================
>> and plot :
>>
>>
>> Traceback (most recent call last):
>>  File "T:\Dropbox\Thèse\Python\fit sonde\test_poly_Tcheb.py", line
>> 32, in <module>
>>    plot (test)
>>  File "C:\Python27\lib\site-packages\matplotlib\pyplot.py", line 2458, in
>> plot
>>    ret = ax.plot(*args, **kwargs)
>>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 3849, in
>> plot
>>    self.add_line(line)
>>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 1443,
>> in add_line
>>    self._update_line_limits(line)
>>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 1451,
>> in _update_line_limits
>>    p = line.get_path()
>>  File "C:\Python27\lib\site-packages\matplotlib\lines.py", line 644,
>> in get_path
>>    self.recache()
>>  File "C:\Python27\lib\site-packages\matplotlib\lines.py", line 401, in
>> recache
>>    y = np.asarray(yconv, np.float_)
>>  File "C:\Python27\lib\site-packages\numpy\core\numeric.py", line
>> 235, in asarray
>>    return array(a, dtype, copy=False, order=order)
>> TypeError: float() argument must be a string or a number
>>
>>
>> ------------------------------------------------------------------------------
>> Write once. Port to many.
>> Get the SDK and tools to simplify cross-platform app development. Create
>> new or port existing apps to sell to consumers worldwide. Explore the
>> Intel AppUpSM program developer opportunity. appdeveloper.intel.com/join
>> http://p.sf.net/sfu/intel-appdev
>> _______________________________________________
>> Matplotlib-users mailing list
>> Mat...@li...
>> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>
>
>
>
> --
> Daniel Hyams
> dh...@gm...
>
> ------------------------------------------------------------------------------
> Write once. Port to many.
> Get the SDK and tools to simplify cross-platform app development. Create
> new or port existing apps to sell to consumers worldwide. Explore the
> Intel AppUpSM program developer opportunity. appdeveloper.intel.com/join
> http://p.sf.net/sfu/intel-appdev
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>

I think that you're misusing Chebyshev (do you really only want to give "3"
as a coefficient..which is just the constant function 3), and you have to
evaluate it in order to give matplotlib some x and y data to plot.

from matplotlib import pyplot as plt
import numpy as np

x = np.linspace(-1.0,1.0)
test = np.polynomial.Chebyshev((1,2,3))
y = test(x)
plt.plot(x,y)
plt.show()



On Tue, Jan 10, 2012 at 9:10 AM, Fabien Lafont <laf...@gm...>wrote:

> I'm trying to plot Chebyshev polynolmials using:
> numpy.polynomial.Chebyshev:
>
>
> import math
> from numpy import *
> from numpy import polynomial as pol
> from pylab import *
> from scipy import *
> from scipy import optimize
> import warnings
> warnings.simplefilter('ignore', np.RankWarning)
>
>
> test = pol.Chebyshev(3)
> print test
> plot (test)
>
>
> show()
> =======================================================================
>
> The print return:      cheb([ 3.])
>
> =======================================================================
> and plot :
>
>
> Traceback (most recent call last):
>  File "T:\Dropbox\Thèse\Python\fit sonde\test_poly_Tcheb.py", line
> 32, in <module>
>    plot (test)
>  File "C:\Python27\lib\site-packages\matplotlib\pyplot.py", line 2458, in
> plot
>    ret = ax.plot(*args, **kwargs)
>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 3849, in
> plot
>    self.add_line(line)
>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 1443,
> in add_line
>    self._update_line_limits(line)
>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 1451,
> in _update_line_limits
>    p = line.get_path()
>  File "C:\Python27\lib\site-packages\matplotlib\lines.py", line 644,
> in get_path
>    self.recache()
>  File "C:\Python27\lib\site-packages\matplotlib\lines.py", line 401, in
> recache
>    y = np.asarray(yconv, np.float_)
>  File "C:\Python27\lib\site-packages\numpy\core\numeric.py", line
> 235, in asarray
>    return array(a, dtype, copy=False, order=order)
> TypeError: float() argument must be a string or a number
>
>
> ------------------------------------------------------------------------------
> Write once. Port to many.
> Get the SDK and tools to simplify cross-platform app development. Create
> new or port existing apps to sell to consumers worldwide. Explore the
> Intel AppUpSM program developer opportunity. appdeveloper.intel.com/join
> http://p.sf.net/sfu/intel-appdev
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>



-- 
Daniel Hyams
dh...@gm...

I'm trying to plot Chebyshev polynolmials using: numpy.polynomial.Chebyshev:


import math
from numpy import *
from numpy import polynomial as pol
from pylab import *
from scipy import *
from scipy import optimize
import warnings
warnings.simplefilter('ignore', np.RankWarning)


test = pol.Chebyshev(3)
print test
plot (test)


show()
=======================================================================

The print return:      cheb([ 3.])

=======================================================================
and plot :


Traceback (most recent call last):
  File "T:\Dropbox\Thèse\Python\fit sonde\test_poly_Tcheb.py", line
32, in <module>
    plot (test)
  File "C:\Python27\lib\site-packages\matplotlib\pyplot.py", line 2458, in plot
    ret = ax.plot(*args, **kwargs)
  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 3849, in plot
    self.add_line(line)
  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 1443,
in add_line
    self._update_line_limits(line)
  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 1451,
in _update_line_limits
    p = line.get_path()
  File "C:\Python27\lib\site-packages\matplotlib\lines.py", line 644,
in get_path
    self.recache()
  File "C:\Python27\lib\site-packages\matplotlib\lines.py", line 401, in recache
    y = np.asarray(yconv, np.float_)
  File "C:\Python27\lib\site-packages\numpy\core\numeric.py", line
235, in asarray
    return array(a, dtype, copy=False, order=order)
TypeError: float() argument must be a string or a number

Hello All, 

I have two questions regarding the matplotlib Slider and animation. 

Question 1: How to create an image along with a Slider axes, such that the Slider values changes with time? 

Here is the example structure of the code I am trying but unsuccessful to have an animated Slider that changes with time.

def complicated_image(Timestep):
	"""Write code to create complicated image where all variables to plot are certain functions of Timestep"""
	p2 = plt.quiver(X,Y,Z1,Z2)
	p3 = plt.pcolormesh(Delta0)
	p1 = plt.contour(r,z,value,10)

	return plt.gca()  [ Question 2 : Is there are better way to return the axis so that it can be used in the animate_image function.]

def animate_image():
	f1 = figure()
	ax = gca()
	
	for i in range(100):
		ax.cla()
		ax = complicated_image(i)
		axtime = plt.axes([0.1,0.01,0.8,0.02],axisbg='white')
		stime = Slider(axtime,'TimeStep',0,100,valinit=0)
		
		f1.savefig('slidertest%03d.png'%i)


If I omit the lines containing the axtime axes (i.e. the part related to Slider) then I get the image properly that changes with time but of course without the Slider.



Regards
Bhargav Vaidya