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Re: discrete numerical 2D gradient


On Tue, Oct 12, 2010 at 1:49 PM, Sebastian Schmitt
<sschmitt at physi.uni-heidelberg.de> wrote:

> I have 2D data represented as a matrix. I would like to obtain the
> gradient.
> ...
> Is there a better (both mathematical and Mathematical) to construct the
> y-derivatives (dyMatrix)?

I would use ListInterpolation on your dataMatrix.  The result is an
InterpolatingFunction that you can manipulate in all sorts of ways.

dataMatrix = Table[i*j, {i, 10}, {j, 10}];
f = ListInterpolation[dataMatrix, {{0, 1}, {0, 1}}];
grad[x_, y_] = {Derivative[1, 0][f][x, y],
   Derivative[0, 1][f][x, y]};
VectorPlot[grad[x, y], {x, 0, 1}, {y, 0, 1}]

Mark McClure


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