[Matplotlib-users] problem plotting large datasets

[Antonio G. <Ant...@ki...>]

Dear all,

I have problems displaying plots for large datasets. Briefly, when attemp=
ting to=20
plot a large number of data points these are not displayed, or only parti=
ally=20
displayed. The simplest way for reproducing my problem is:

   from pylab import *
   datalen =3D 100000

   data =3D rand(datalen)
   plot(data)
   show()

Here, if datalen is 10000, then the graph looks as expected. However, if =
datalen=20
is increased, say, to 100000, then the resulting plot is incomplete (as s=
hown in=20
snapshot1). Moreover, when trying to zoom, the axes display the new value=
s=20
reflecting the zoomed scale, but the data are not actually zoomed (eg=20
snapshot2). I have no clue as to what can be wrong, since no error is ret=
urned.=20
Also, no error results from running the example above with --verbose-help=
ful:

   antonio@linux:~/python> python test.py --verbose-helpful
   matplotlib data path /usr/lib/python2.4/site-packages/matplotlib/mpl-d=
ata
   $HOME=3D/home/antonio
   CONFIGDIR=3D/home/antonio/.matplotlib
   loaded rc file /home/antonio/.matplotlib/matplotlibrc
   matplotlib version 0.88svn
   verbose.level helpful
   interactive is False
   platform is linux2
   numerix numpy 0.9.6.2206
   font search path ['/usr/lib/python2.4/site-packages/matplotlib/mpl-dat=
a']
   loaded ttfcache file /home/antonio/.matplotlib/ttffont.cache
   backend TkAgg version 8.4

In a real example of what I'm trying to do: I read a fragment of data fro=
m a=20
large file, then plot such fragment of data; convolve it and plot the res=
ult (as=20
in snapshot3); interactively make some decisions according to such plot, =
and=20
then move to the next fragment of my large file to repeat the process. Ho=
wever,=20
whenever I attempt to plot large chunks of data, the plot is not displaye=
d (eg=20
snapshot4). As mentioned, no error is returned, and thus I have no clue a=
s to=20
how to fix this problem.

(For the record, in snapshot3 the length of data plotted is 671334 [top] =
and=20
132829 [bottom]. In snapshot4 it is 1162554 [top] and 231073 [bottom].)

Any help will be much appreciated.

Antonio



--=20
Antonio Gonzalez, MD MSc PhD
Department of Neuroscience
Karolinska Institutet
Retzius v=C3=A4g. 8
171 77 Stockholm
Sweden