On 5/21/10 3:57 PM, Benjamin Root wrote:
I did some more digging and I think I have a hypothesis for what is
happening.
There is only one main difference between a call to .drawstates() and
.readshapefiles() with respect to loading and plotting data.
.drawstates() loads *only* the line segments that coincide with the
defined map boundaries, while .readshapefiles() loads all of the data
in the shapefile. Therefore, the LineCollection that gets attached to
the axis contains data from outside the stated domain.
In addition, the basemap versions of the plotting functions have the
benefit of finishing their calls with a call to .set_axes_limits(),
which keeps the axes in check. However, a non-basemap version would
not call that automatically, thereby having its axes automatically
expanded to contain all of the data in the LineCollection.
I am not sure what exactly should be done about this. This is
certainly un-intuitive behavior, though. Maybe there could be a
keyword option in .readshapefile() to have only the data for the
stated domain loaded? That might solve the issue.
Thanks,
Ben Root
Ben: That's why you should use the basemap methods where possible (they
handle these things for you). You could also turn autoscaling off on
your axes using
ax.set_autoscaleon(False)
and then they won't automatically expand when you plot data outside your
map region. Or, you could just call the set_axes_limits() methods
before you draw the plot.
Clipping the polygons to the map projection region is non-trivial, and I
don't think I want to add that to readshapefile.
-Jeff
On Fri, May 21, 2010 at 4:08 PM, Benjamin Root <ben.r...@ou.edu
<mailto:ben.r...@ou.edu>> wrote:
Hello,
I have been tracking down an annoying (but easily worked around)
issue with Basemap. It seems that if you call .readshapefile() to
create, for example, roads on your image, and then call any pyplot
command afterwards for that axis, the axis will reset itself to
the entire domain (I guess it would be the complete domain stated
in the shapefile, maybe?). This does not happen if you call the
equivalent function from the Basemap instance, though. Also, this
does not happen with drawstates() and its ilk.
I have made a test script and a couple of supporting shapefile in
a tar.gz file to demonstrate the issue. It is available here:
http://dl.dropbox.com/u/7325604/basemaptest.tar.gz
I have also attached a png file showing the resulting image as it
appears on my computer. I have no clue as to the cause and I hope
that someone here might have an idea.
Thanks,
Ben Root
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