Thank you for your answer. I've read the numpy tutorial and I get it that array and matrices behave differently.
Now, what I find kind of strange is that the plot I get when directly feeding the matrices to scatter doesn't really seem to represent anything. I think that, if possible, showing an error or a warning would be much more appropriate than showing a plot. It would let the user know that the problem is not with her dataset, but with the plot. Wouldn't it be possible to simply check the shape in scatter() and display a warning if it has more than one dimension ? Best, Julien On Tue, Mar 20, 2012 at 3:52 PM, Jerzy Karczmarczuk <jerzy.karczmarc...@unicaen.fr> wrote: > LJulien Rebetez : >> I've run into a strange behaviour of matplotlib while trying to figure >> out why my data was displayed incorrectly. >> I'm note quite sure if this is a bug or expected behaviour, but I feel >> it's kind of counter-intuitive, so I'm posting here. >> >> ... >> Now there seem to be a difference on how numpy handles A[:,0] >> depending on if A is a np.array or np.matrix. In the case of >> an array, a 1D array is returned, in the case of a matrix, a 2D Nx1 >> matrix is returned. Using this matrix seems to confuse matplotlib. >> >> Using np.ravel or np.flatten on the slices fix that problem. >> >> Is there an explanation for this behaviour or should I fill a bug ? > Don't fill a bug. > Read http://www.scipy.org/Tentative_NumPy_Tutorial , please. > They explain that a slice of a matrix is a matrix, and its "view" is > different from what you get for arrays. > > But, no need to reshape the stuff. Just use the "array attribute" of the > matrix : > > pl.scatter(B.A[:,0], B.A[:,1], c='b') > > //Here 'A' is the name of the attribute, nothing to do with your array > A; by chance it is the same...// > > > The best > > Jerzy Karczmarczuk > > > ------------------------------------------------------------------------------ > This SF email is sponsosred by: > Try Windows Azure free for 90 days Click Here > http://p.sf.net/sfu/sfd2d-msazure > _______________________________________________ > Matplotlib-users mailing list > Matplotlib-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/matplotlib-users ------------------------------------------------------------------------------ This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
