Get contour matrix without plotting?

I have a big gridded dataset Z and I want to create a contour matrix C from it. I need contours at many levels, -100:2:100. I can do this:

C = contour(Z,100:2:100);

Unfortunately, computation time is slow, it takes several minutes because my Z is large and I am trying to get a lot of countour lines out of it. How can I speed this up? I was hoping I could get C without plotting, but I don't know how to do that. I tried turning the figure visibility off but that had only a quarter of a second improvement out of several minutes computation time.

Ideas?

[Chad Greene]

Any tips for speeding up the acquisition of C?

Answer 1

[Moritz]

Have you tried contourc instead of contour ? It gives you the contour lines without any plots.

[cline]=contour(Z,[1 1]); gives you one contour line at level 1 Of course you can do many levels.

With one level: cline(1,2:end) contains your x values cline(1,1) contains the level cline(2,1) contains the numer of data poinst cline(2,2:end) contains your corresponding y values

with multiple values it just adds the new level at the end of the array, you can find it by the entry of it´s level

[Chad Greene]

This is exactly what I was seeking. Thank you so much!

[Chad Greene]

I have uploaded the solution to FEX: