Get contour matrix without plotting?
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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?
Accepted Answer
Moritz
on 20 Sep 2013
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
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