On 12/27/11 12:07 PM, Logi Ragnarsson wrote: > Hello, > > Is it supposed to be possible to do a filled contour plot with alpha > levels in the colour map? I'm plotting weather data on top of maps and > would very much like to plot low levels of wind and precipitation as > mostly transparent, with higher levels more opaque. > > If I replace the meat of the plotting code with these two lines: > > basemap.bluemarble() > basemap.contourf(x, y, precipitation, > colors=colorConverter.to_rgba_array([ > # no colour for zero -> fully transparent > (1,0,0,0.5), > (0,1,0,1), > (0,1,1,0.5), > (0,0,1,1), > (1,0,1,0.5) > ]), levels=[ > # no level for zero -> fully transparent > 0.001, > 0.01, > 0.1, > 1, > 10 > ]) > > I end up with the (deliberately) pretty horrible looking plot in the > attachment. The alpha values in the colors argument are completely > ignored, but having no colour specified for values below 0.001 (mm/hr) > causes those areas to be left transparent. I'm plotting the Blue > Marble simply to have something visible under the weather plot. > > Is this supposed to work at all in any way? > > I'm using matplotlib 1.1.0 and basemap 1.0.2 on debian with the 'Agg' > back-end. The data being plotted is a netCDF dataset read from the > output of the WRF weather model. > > Regards, > Logi >
Logi: It looks like alpha transparency is controlled with the alpha keyword, so you can't specify different alphas for each contour level. You may have to call contourf multiple times, changing the alpha as needed for each set of contour levels. -Jeff ------------------------------------------------------------------------------ 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 Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
