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Viewing a Penny

This example shows four techniques to visualize the surface data of a penny. The file PENNY.MAT contains measurements made at the National Institute of Standards and Technology of the depth of the mold used to mint a U. S. penny, sampled on a 128-by-128 grid.

Drawing a Contour Plot

Draw a contour plot with 15 copper colored contour lines.

load penny.mat
contour(P,15)
colormap(copper)
axis ij square

Drawing a Pseudocolor Plot

Draw a pseudocolor plot with brightness proportional to height.

pcolor(P)
axis ij square
shading flat

Drawing a Pseudocolor Plot With a Colormap

Draw a pseudocolor plot with brightness proportional to the Laplacian of the height. A cell is bright if its height is greater than the average of its four neighbors and dark if its height is less than the average of its four neighbors. This is an unusual "lighting model", but it produces an image that looks like a photograph of a penny.

D = -del2(P);
pcolor(D)
axis ij square
shading flat

Drawing a Surface Plot With a Colormap

Finally, produce a 3-D, copper colored, surface plot with the Laplacian lighting model.

surf(P,D);
axis('ij','tight')
shading('flat')
view(-20,75)

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