Derivative of contour line with specific values

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Hi igor Folks,

I have an imagery data, say, 1000 (x-axis) by 2000 (y-axis) pixels with data values ranging from 0 to 1. Is there an easy way to find the 2nd derivative (either y vs x or x vs y) of a specific contour line with constant value of 0.5? In other words, I wish to quantify the curvature of the contour lines with various values (levels); some contour lines are more straight and others are more "irregular" with more curvatures. Any suggestions will be greatly appreciated!

zh
The first part of the problem is solved by extracting the X Y wave pair that corresponds to a contour trace in a contour plot. For that, see the WaveMetrics procedure Extract Contours As Waves.ipf. An easy way to get there is to view the WM Procedures Index help file:

DisplayHelpTopic "WaveMetrics Procedures"

Extract Contours as Waves is described in a subsection of that help file:

DisplayHelpTopic "Image and Contour Plots"

Find the description of Extract Contours as Waves, then click the button that doesn't have the red X on it. That will put a #include line into your main Procedure window, and show you the code window. There are comments at the top that describe what's in the file.

John Weeks
WaveMetrics, Inc.
support@wavemetrics.com

October 2, 2014 at 09:51 am - Permalink

John,

Thank you so much for your quick reply. I have found the file you mentioned and will look at it.
You, Howard and other Wavemetrics guys are doing a great job in helping customers in solving all kinds of problems.

Cheers,
zh

October 3, 2014 at 09:46 am - Permalink