[SciPy-user] drawing time

[Travis E. Oliphant]

Johannes Broedel wrote:

> Hallo,
>
> thanks for the short progrma, trying ade my computer producing the 
> following message (IPython):
>
> In [7]: run sciptest.py
> --------------------------------------------------------------------------- 
>
> MemoryError                               Traceback (most recent call 
> last)
>
> /home/jbroedel/python/graphtest/sciptest.py
>      5 xplt.hold('on')
>      6 for xval in x:
>      7       yval = sin(xval / 4)
> ----> 8       xplt.plot(xval, yval, 'x')
>      9       xplt.pause(100)
>
> /home/python/PYTHON/lib/python2.2/site-packages/scipy/xplt/Mplot.py in 
> plot(x, *args, **keywds)
>    480             y = scipy.real(y)
>    481         y = where(scipy.isfinite(y),y,0)
> --> 482         
> gist.plg(y,x,type=thetype,color=thecolor,marker=themarker,marks=tomark,width=linewidth) 
>
>    483
>    484         nowplotting = nowplotting + 1


This looks the problem I had when I first tried the little test program. 
 For me, it was because y and x are scalars (not 1-d arrays) (and the 
xplt.plot program uses squeeze so that even if you try to give it [x] it 
will turn the 1-d array with one element into a scalar).

Gists plg can't use scalars.  This xplt.plot problem was fixed in CVS 
two days ago.

>
> MemoryError:
> WARNING: Failure executing file: <sciptest.py>
>
> The real problem I had was with the following program:
>
> #!/usr/bin/env python
>
> from Numeric import *
> from scipy.xplt import *
>
>
> def standard_map(x_cor,y_cor,kappa):
>    """provide one interate of the inital conditions x_cor,y_cor
>       for the standard map with parameter kappa.
>    """
>    y_cor_new=(y_cor-kappa*sin(2.0*pi*x_cor) )% 1
>    x_cor_new=(x_cor+y_cor_new )   % 1
>
>    return(x_cor_new,y_cor_new)


The code you had worked for me on my system (I'm not sure what it's 
supposed to do, but it generated points on the page).

A couple of things (aside from the indentation problems I had when your 
code came through the email)

1) I would recommend using plot instead of plg.  Plot hides some of the 
oddities and use a MATLAB-style syntax
      for plottin characters.

2) I wouldn't use points for a test like this (they can be very hard to 
see).  I used the following code:


if __name__ == '__main__':
   window()             # initialize plotting
   limits(0.0,1.0,0.0,1.0)
   x,y=0.5,0.1          # initial (x,y)
   k=1.1/(2.0*pi)       # parameter
   animate(0)
   iterations=1000
   xplt.hold('off')
   xplt.fma()
   xplt.hold('on')
   while 1:             # iterate initial conditions
       for i in range(iterations):
           (x,y)=standard_map(x,y,k)
           plot(x,y,'bx')                                       # The b 
means blue, the x means make an x symbol at the point.
           ch=mouse(-1,0,"press mouse button")
           x,y=ch[0],ch[1]
           if(ch[9]==3): break  # mouse key 3
       plg(array([y]),array([x]))   # I don't now what this is supposed 
to do.


-Travis O.