Yannick Copin wrote: > Hi, > > Eric Firing wrote: >>> from pylab import * >>> X, Y = meshgrid(linspace(-3,3,11),linspace(-3,3,11)) >>> Z = randn(*X.shape) >>> lev = linspace(Z.min(),Z.max(),11)[1:-1] >>> contourf(X,Y,Z, lev, extend='both') >>> contour(X,Y,Z, lev, colors='k') >>> show() >> >> Now, you may be wondering why we can't simply use the boundary of the >> filled regions for the lines as well, to guarantee they are the same. >> The reason is that filled contour boundaries include cuts connecting >> inner and outer contours, and also inner boundaries (edges of masked >> regions--except when affected by a bug) and the outer boundaries of >> the domain). It might be possible to simply exclude those line >> segments from the line contours, but it is not clear to me that the >> effort would be well-spent. > > OK, thanks for the explanations. I was using this dual approach > contourf+contour to emphasize the contours from contourf. So is there a > direct way to set the linewidth and linecolor (and linestyle?) of > contours from contourf? (I suspect not, according to contourf > documentation: > > contourf differs from the Matlab (TM) version in that it does not > draw the polygon edges, because the contouring engine yields > simply connected regions with branch cuts. To draw the edges, > add line contours with calls to contour. > > ) >
You could turn on coloring of the edges, but I don't think you would like the result because the edges would include the boundary lines and the cut lines. The ContourSet object returned by contour and contourf has a .collections attribute. For contourf it is a list of PolyCollections, and you can set their attributes. >> I think that the differences illustrated in your example will occur >> almost entirely in pathologically ambiguous cases, but it is also > > Not necessarily pathological cases, just noisy data :-/ (I agree my > randn-based example was a bit extreme!) You might be able to avoid the problem most of the time by using some gridding routine, preferably something that uses a bit of curvature, to double the number of points in each dimension. I haven't tried it, but I suspect that this would turn even a very noisy field into something that would be contoured the same by contour and contourf. > > Cheers. ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
