Re: [Matplotlib-users] plotting a contour of gridded data

[Peter I. H. <pe...@gm...>]

On 7/11/07, Eric Firing <ef...@ha...> wrote:
> Peter I. Hansen wrote:
> > Hello
> >
> > I have gridded data of the shape:
> >
> > x_1 y_1 z_1
> > x_1 y_2 z_2
> > .       .       .
> > x_1 y_N z_N
> >
> > x_2 y_1 z_(N+1)
> > x_2 y_2 z_(N+2)
> > .       .       .
> > x_2 y_N z_(2N)
> >
> > x_M y_1 z_(MN)
> > x_M y_2 z_(MN)
> > .        .      .
> > x_M y_N z_(MN)
> >
> > I've tried to follow the contour_demo script by making
>
>
> You don't need to make your own X, Y, so delete the following 3 lines.
> >
> > x = arange(M numbers)
> > y = arange(N numbers)
> > X,Y = meshgrid(x,y)
> >
> > M = load('zdata.dat')
>
> Now you have X, Y, and Z, each as a column in your file, so you need to
> split them apart and reshape them.  Let's assume M, N are the number of
> X and Y values in your grid; to avoid name confusion, change the load to
>
> XYZ = load('zdata.dat')
>
> X = XYZ[:,0]
> X.shape = (M,N)
> Y = XYZ[:,1]
> Y.shape = (M,N)
> Z = XYZ[:,2]
> Z.shape = (M,N)
>
> CS = contour(X.transpose(), Y.transpose(), Z.transpose())
>
> The reason for all the transposing is that pcolor and contour display
> images with column number increasing with X, and row number increasing
> with Y.  Since you have M X-values and N Y-values, everything has to end
> up N by M, not the reverse.

Perfect. That was just what i needed to know. Thanks!