matplotlib-devel Mailing List for matplotlib

Hi

I have found a problem when using external color information to color 
the arrows in a quiver-plot. I found that the norm-option does not 
affect the output. Here is the code I chanegd to fix this problem (3 
lines, marked with a #PI).

Pierre

--- fragment of file axes.py: ---

    def quiver(self, U, V, *args, **kwargs ):
        """
        QUIVER( X, Y, U, V )
        QUIVER( U, V )
        QUIVER( X, Y, U, V, S)
        QUIVER( U, V, S )
        QUIVER( ..., color=None, width=1.0, cmap=None,norm=None )

        Make a vector plot (U, V) with arrows on a grid (X, Y)

        The optional arguments color and width are used to specify the 
color and width
        of the arrow. color can be an array of colors in which case the 
arrows can be
        colored according to another dataset.

        If cm is specied and color is None, the colormap is used to give 
a color
        according to the vector's length.

        If color is a scalar field, the colormap is used to map the 
scalar to a color
        If a colormap is specified and color is an array of color 
triplets, then the
        colormap is ignored

        width is a scalar that controls the width of the arrows

        if S is specified it is used to scale the vectors. Use S=0 to 
disable automatic
        scaling.
        If S!=0, vectors are scaled to fit within the grid and then are 
multiplied by S.


        """
        if not self._hold: self.cla()
        do_scale = True
        S = 1.0
        if len(args)==0:
            # ( U, V )
            U = asarray(U)
            V = asarray(V)
            X,Y = meshgrid( arange(U.shape[1]), arange(U.shape[0]) )
        elif len(args)==1:
            # ( U, V, S )
            U = asarray(U)
            V = asarray(V)
            X,Y = meshgrid( arange(U.shape[1]), arange(U.shape[0]) )
            S = float(args[0])
            do_scale = ( S != 0.0 )
        elif len(args)==2:
            # ( X, Y, U, V )
            X = asarray(U)
            Y = asarray(V)
            U = asarray(args[0])
            V = asarray(args[1])
        elif len(args)==3:
            # ( X, Y, U, V )
            X = asarray(U)
            Y = asarray(V)
            U = asarray(args[0])
            V = asarray(args[1])
            S = float(args[2])
            do_scale = ( S != 0.0 )

        assert U.shape == V.shape
        assert X.shape == Y.shape
        assert U.shape == X.shape

        arrows = []
        N = sqrt( U**2+V**2 )
        if do_scale:
            Nmax = maximum.reduce(maximum.reduce(N))
            U *= (S/Nmax)
            V *= (S/Nmax)
            N /= Nmax

        alpha = kwargs.get('alpha', 1.0)
        width = kwargs.get('width', 0.25)
        norm = kwargs.get('norm', None)
        cmap = kwargs.get('cmap', None)
        vmin = kwargs.get('vmin', None)
        vmax = kwargs.get('vmax', None)
        color = kwargs.get('color', None)
        shading = kwargs.get('shading', 'faceted')

        C = None
        I,J = U.shape
    colorarrayflag = False #PI
        if color is not None and not looks_like_color(color):
            clr = asarray(color)
            if clr.shape==U.shape:
                C = array([ clr[i,j] for i in xrange(I)  for j in 
xrange(J)])
        colorarrayflag = True #PI
            elif clr.shape == () and color:
                # a scalar (1, True,...)
                C = array([ N[i,j] for i in xrange(I)  for j in xrange(J)])
            else:
                color = (0.,0.,0.,1.)
        elif color is None:
            color = (0.,0.,0.,1.)
        else:
            color = colorConverter.to_rgba( color, alpha )


        arrows = [ Arrow(X[i,j],Y[i,j],U[i,j],V[i,j],0.1*S ).get_verts()
                   for i in xrange(I) for j in xrange(J) ]
        collection = PolyCollection(
            arrows,
            edgecolors = 'None',
            facecolors = (color,),
            antialiaseds = (0,),
            linewidths = (width,),
            )
        if C is not None:
            collection.set_array( C )
        else:
            collection.set_facecolor( (color,) )
        collection.set_cmap(cmap)
        collection.set_norm(norm)
        if norm is not None and colorarrayflag==False: # PI
            collection.set_clim( vmin, vmax )
        self.add_collection( collection )
        lims = asarray(arrows)
        _max = maximum.reduce( maximum.reduce( lims ))
        _min = minimum.reduce( minimum.reduce( lims ))
        self.update_datalim( [ tuple(_min), tuple(_max) ] )
        self.autoscale_view()
        return arrows