Ryan May wrote: > On Fri, Apr 2, 2010 at 11:42 AM, Eric Firing <efir...@hawaii.edu> wrote: >> Ryan May wrote: >>> On Fri, Apr 2, 2010 at 1:23 AM, Eric Firing <efir...@hawaii.edu> wrote: >>>>> On Fri, Mar 26, 2010 at 12:13 PM, Ryan May <rma...@gmail.com> wrote: >>>>>> I just hit a problem with using quiver with Basemap when when >>>>>> angles='xy'. Because Basemap's x,y units are in meters, you end up >>>>>> with angles that are quantized due to floating point truncation >>>>>> (30000. + 0.001*u = 30000.). Changing to angles='uv' fixes the >>>>>> problem, but it probably should be automatically scaled, as noted in >>>>>> the comments: >>>>>> >>>>>> elif self.angles == 'xy' or self.scale_units == 'xy': >>>>>> # We could refine this by calculating eps based on >>>>>> # the magnitude of U, V relative to that of X, Y, >>>>>> # to ensure we are always making small shifts in X, Y. >>>>>> >>>>>> I managed to fix the problem locally by setting: >>>>>> >>>>>> angles, lengths = self._angles_lengths(U, V, eps=0.0001 * >>>>>> self.XY.max()) >>>>>> >>>> I don't think this will work in all cases. For example, there could be a >>>> single arrow at (0,0). >>> Good point. >>> >>>> Instead of self.XY.max(), how about abs(self.ax.dataLim.width)? >>> Wouldn't this have problems if we zoom in sufficiently that the width >>> is much less than magnitude of the values? Not exactly sure what data >>> set would sensibly yield this, so I'm not sure if we should worry >>> about it. >>> >>> If we do care, we could just put a minimum bound on eps: >>> >>> eps=max(1e-8, 0.0001 * self.XY.max()) >> I don't like taking the max of a potentially large array every time; and one >> needs max absolute value in any case. I think the following is better: >> >> eps = np.abs(self.ax.dataLim.extents).max() * 0.001 > > I hadn't thought about performance. I think that's more important > than any worries about bounds being disproportionately smaller. I'll > check this in.
Sorry for the piecemeal approach in thinking about this--but now I realize that to do this right, as indicated by the comment in the original code, we need to take the magnitude of U and V into account. The maximum magnitude could be calculated once in set_UVC and then saved so that it does not have to be recalculated every time it is used in make_verts. Maybe I am still missing some simpler way to handle this well. Eric > > Ryan > ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Matplotlib-devel mailing list Matplotlib-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-devel
