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Re: How to obtain contour data through contour command? [message #86283 is a reply to message #86263]

Tue, 22 October 2013 14:50

kagoldberg
Messages: 26
Registered: November 2012

Junior Member

An example of looks like this

contour, image, levels=[30.,40.], path_info=pinfo, path_xy=pxy, /path_data_coords, /closed

Here, pinfo is a structure that tells you about the information contained in pxy.
You have to write some flexible code to handle this properly because pxy is a single, 2xN array that actually contains all of the contours you requested, strung together vertically. pxy[0,*] are the x values, and pxy[1,*] are the y values.

To make it usable, you have to sort through pinfo. pinfo is an array of structures with fields {type, high_low, level, n, offset, value}. The pinfo.offset field elements tell you the index values of pxy where each contour starts, and pinfo.n elements tell you how many points are in each contour.

Here is one array for each contour.
xy0 = pxy[0:1, pinfo[0].offset : pinfo[0].offset + pinfo[0].N - 1]
xy1 = pxy[0:1, pinfo[1].offset : pinfo[1].offset + pinfo[1].N - 1]

Where you have to be careful, I've found, is that sometimes you get two (or more?) contours for the same level value. In my example I have 2 levels, but you could end up with 3 or more contour "pieces." So check the pinfo.value field to see if you have separate contours with matching level values, and group/concatenate them if necessary.

-Ken

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[Message index]

		How to obtain contour data through contour command? By: jacobsvensmark on Tue, 22 October 2013 05:12
		Re: How to obtain contour data through contour command? By: Mats Löfdahl on Tue, 22 October 2013 06:14
		Re: How to obtain contour data through contour command? By: David Fanning on Tue, 22 October 2013 06:32
		Re: How to obtain contour data through contour command? By: kagoldberg on Tue, 22 October 2013 14:50

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