Is there a way to get a contour plot with different sections of a single contour line having different colors, based on some extra information other than X,Y,Z data?

I have to plot contour lines with X,Y,Z data and another data set W, which will decide what color that particular set of X,Y,Z data point in the contour should have.

Example:

level = [0 0];
contour(X,Y,Z,level)
% Here i don't want an isoline to have the same color all throughout.

I have an extra data set W of the same dimension as X,Y,Z. And depending on the value of W, I want to select a specific color for that particular point X,Y,Z in the contour line. How do I accomplish that?

Answer 1

[Walter Roberson]

Get it to return the contour matrix instead of drawing. The contour matrix is described at http://www.mathworks.com/help/matlab/ref/contour-properties.html#prop_ContourMatrix . Then use that contour matrix and your additional data to draw the lines you want.

You will probably want to use patch() to draw the contour lines, and use edgecolor 'flat' or 'interp', having written color information into CData or FaceVertexCData. Vertices will not necessarily be exactly pixel coordinates so you might want to use interp2 to look up values from your W matrix.

[Shini Bhatt]

I am not really sure how to do that. Can you provide an example on what you are suggesting?

[Walter Roberson]

Call contourc to get the contour matrix without plotting.

You can use one of

http://www.mathworks.com/matlabcentral/fileexchange/43162-c2xyz-contour-matrix-to-coordinates

or

http://www.mathworks.com/matlabcentral/fileexchange/38863-extract-contour-data-from-contour-matrix-c

to assist in extracting the data from the contour matrix.

For more about coloring the edges, see

http://www.mathworks.com/help/matlab/visualize/specifying-patch-coloring.html#f2-12890

http://www.mathworks.com/matlabcentral/newsreader/view_thread/269822