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Slice contour graphic at given level

I have the following function (z) that should output a graphic which if sliced at f(x,y) = 0.001 the result image should be a message.

I wrote this code but I`m unable to slice it right

[x,y] = meshgrid(-1.5:0.3:1.5,-2.5:0.5:2.5) ;
z=exp(-4*x.^2-2*y.^2)*cos(8*x)+exp(-3*((2*x+1)/2).^2-6*y.^2);           
% meshc (x,y,z, [0.001 0.001]);

meshc (x,y,z);

What did i miss?

Solution

  • You are likely looking for the countour function instead of meshc. meshc plots a contour plot under a mesh plot, but you don't need a mesh plot to view the message. In fact, the countour docs show an example of how to only plot a specific level:

    contour(x, y, z, [0.001 0.001])

    I also suspect that your function is not defined correctly. exp(...) * cos(...) should probably read exp(...) .* cos(...):

    enter image description here

    The poor granularity leads me to believe that the sample spacing should be decreased (i.e., the grid should be made finer):

    [x,y] = meshgrid(-1.5:0.003:1.5,-2.5:0.005:2.5);

    enter image description here

    Contouring the original function with the finer spacing also shows why I think * should probably be .* in the expression:

    [x,y] = meshgrid(-1.5:0.003:1.5,-2.5:0.005:2.5);
z=exp(-4*x.^2-2*y.^2)*cos(8*x)+exp(-3*((2*x+1)/2).^2-6*y.^2);
contour(x, y, z, [0.001 0.001])

    enter image description here

    Unless the message is a count of sausage shapes, I think that the .* version is more likely to contain useful information (looks like HI).