# Slow drawing of many lines in Basemap

I'm drawing several hundred lines at a time, each consisting of 10-100 points, and it takes a couple of minutes for them all to display, which makes me think I must be doing something stupid.

The function that does the drawing looks like this:

def plotlinmap(lins, map=None):
if map is None:
map = Basemap()

map.drawmapboundary(fill_color="white")
map.drawmeridians(range(-180,181,30)), labels=[1,0,0,1])
map.drawparallels(range(-90,91,30)), labels=[1,0,0,1])

for lin in lins:
x,y = map(degrees(lin.longitudes()),degrees(lin.latitudes()))
map.plot(x,y)

return(map)

It displays one line at a time, whenever map.plot() is called. Really I'd like it to just do all the drawing at the end (assuming that would make the whole process much faster). Is there some way to cleanly pass map.plot() a big list of lines to draw? I'm sure there is and I'm just being dense. Argh.

···

--
Zane Selvans
Amateur Earthling
http://zaneselvans.org
zane@...1923...
303/815-6866
PGP Key: 55E0815F

Zane Selvans wrote:

I'm drawing several hundred lines at a time, each consisting of 10-100 points, and it takes a couple of minutes for them all to display, which makes me think I must be doing something stupid.

The function that does the drawing looks like this:

def plotlinmap(lins, map=None):
if map is None:
map = Basemap()

map.drawmapboundary(fill_color="white")
map.drawmeridians(range(-180,181,30)), labels=[1,0,0,1])
map.drawparallels(range(-90,91,30)), labels=[1,0,0,1])

for lin in lins:
x,y = map(degrees(lin.longitudes()),degrees(lin.latitudes()))
map.plot(x,y)

return(map)

It displays one line at a time, whenever map.plot() is called. Really I'd like it to just do all the drawing at the end (assuming that would make the whole process much faster). Is there some way to cleanly pass map.plot() a big list of lines to draw? I'm sure there is and I'm just being dense. Argh.

--
Zane Selvans
Amateur Earthling
http://zaneselvans.org
zane@...1923...
303/815-6866
PGP Key: 55E0815F

Zane: You can set up a LineCollection like this

lcoll = LineCollection(segments)

then add it to the current axes

ax = pylab.gca()

(instead of using the Basemap plot method).

To make sure the map axes are rescaled properly, you may need to do

map.set_axes_limits()

afterwards.

See the line_collection.py pylab example for more details.

-Jeff

···

--
Jeffrey S. Whitaker Phone : (303)497-6313
NOAA/OAR/CDC R/PSD1 FAX : (303)497-6449
325 Broadway Boulder, CO, USA 80305-3328

It turned out that just adding:

interactive(False)

before the drawing loop, and

show()

after it, sped things up tremendously. Instead of 5 minutes, it now takes about 2 seconds for the map to render. Which, ironically, is much more "interactive"

Thanks for the pointer to LineCollection though. I'd never seen that.

Zane

···

On Aug 22, 2008, at 5:08 AM, Jeff Whitaker wrote:

Zane Selvans wrote:

I'm drawing several hundred lines at a time, each consisting of 10-100 points, and it takes a couple of minutes for them all to display, which makes me think I must be doing something stupid.

Zane: You can set up a LineCollection like this

lcoll = LineCollection(segments)

then add it to the current axes

ax = pylab.gca()