From: Tim Michelsen <timmichelsen@gm...> - 2008-09-29 20:06:53
Hello users and developers of matplot,
I would like to ask what kind of interpoaltion method is used by
I suppose that it uses linear interpolation to derive the areas between
the contour lines.
Is that true?
From: Eric Firing <efiring@ha...> - 2008-09-29 20:30:05
Tim Michelsen wrote:
> Hello users and developers of matplot,
> I would like to ask what kind of interpoaltion method is used by
> I suppose that it uses linear interpolation to derive the areas between
> the contour lines.
> Is that true?
> Kind regards,
I am not sure exactly what you are asking. General contouring routines,
such as the one in mpl, work by subdividing the domain into a set of
contiguous polygons, calculating the points at which contours cross
boundaries, and then connecting these points, usually with straight
lines. Routines differ in the methods used to subdivide the domain and
in the methods used to connect the points, since this can be ambiguous.
The cntr.c code in mpl subdivides the domain into the rectangles given
by the quadrilateral grid on which the data are provided. In contrast,
some other routines divide each such rectangle into 4 triangles by
interpolating a point in the middle.
If you want to contour data that are not on a regular grid, or that are
on a regular but coarse grid, or that are too noisy to be contoured
nicely (assuming the noise has a small scale relative to the scale of
the signal), then you need to use a gridding routine of your choice
before contouring. It is the job of the gridding routine to do any
necessary interpolation and/or smoothing.