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POmatplotlib - extracting data from contour lines
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  1. POmatplotlib - extracting data from contour lines
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    copied!<p>I would like to get data from a single contour of evenly spaced 2D data (an image-like data).</p> <p>Based on the example found in a similar question: <a href="https://stackoverflow.com/q/1560424/429795">How can I get the (x,y) values of the line that is ploted by a contour plot (matplotlib)?</a> </p> <pre><code>&gt;&gt;&gt; import matplotlib.pyplot as plt &gt;&gt;&gt; x = [1,2,3,4] &gt;&gt;&gt; y = [1,2,3,4] &gt;&gt;&gt; m = [[15,14,13,12],[14,12,10,8],[13,10,7,4],[12,8,4,0]] &gt;&gt;&gt; cs = plt.contour(x,y,m, [9.5]) &gt;&gt;&gt; cs.collections[0].get_paths() </code></pre> <p>The result of this call into <code>cs.collections[0].get_paths()</code> is:</p> <pre><code>[Path([[ 4. 1.625 ] [ 3.25 2. ] [ 3. 2.16666667] [ 2.16666667 3. ] [ 2. 3.25 ] [ 1.625 4. ]], None)] </code></pre> <p>Based on the plots, this result makes sense and appears to be collection of (y,x) pairs for the contour line. </p> <p>Other than manually looping over this return value, extracting the coordinates and assembling arrays for the line, are there better ways to get data back from a <code>matplotlib.path</code> object? Are there pitfalls to be aware of when extracting data from a <code>matplotlib.path</code>?</p> <p>Alternatively, are there alternatives within <code>matplotlib</code> or better yet <code>numpy</code>/<code>scipy</code> to do a similar thing? Ideal thing would be to get a high resolution vector of (x,y) pairs describing the line, which could be used for further analysis, as in general my datasets are not a small or simple as the example above.</p>
 

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