Color Contours along a Line

Hello, I'm trying to create color contours along a straight line, yet I'm running into a lot of difficulty. I want to specify an x-coordinate and y-coordinate at the beginning and end of some line and then have a different color show up on that line based on some relative values. For example, I have a line from [0,-15] to [4,15] and would like to contour a color based on the fact that at [0,-15] I have a value 0.75 and at [4,15] I have a value of 0.25. I have been trying to use the built-in Matlab function 'contour' but have been unsuccesful as the Z data (i.e., my 0.75 and 0.25) is required to be a minimum of a 2x2 matrix.

Any help would be greatly appreciated, even if the best answer is "you can't do that with the 'contour' function"...

Thanks in advance!

~Cliff

Answer 1

[Walter Roberson]

You can't do that with contour.

What you are asking for is not contour but color interpolation. Ordinary MATLAB line and lineseries objects (such as are created by plot()) cannot have multiple colors.

Probably the easiest method to achieve the effect you want is to patch() between the two points, setting cdata to the colors you want, and setting EdgeColor to 'interp'. You might find it easiest to use explicit Vertex and Face specification:

patch('Vertices', [0 -15; 4 15], 'Faces', [1 2], 'FaceVertexCData', [0.75; 0.25], 'EdgeColor', 'interp')

[Cliff]

Thanks Walter! This is a big help!

~Cliff

[Cliff]

This is actually working pretty well; thanks again! One follow-up question: I'm trying to change the line thickness by adding (...,'LineWidth',5) to the code you have above, but that doesn't seem to work. If I swap 'interp' to 'flat', then I get the increased line width, but obviously not the color interpolation that I want. Is this a limitation in Matlab or am I doing someting incorrectly?

Thanks again,

~Cliff