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    <p>This is is a late response, perhaps, but it was the first hit when I Googled 'numpy line intersections'. In my case, I have two lines in a plane, and I wanted to quickly get any intersections between them, and Hamish's solution would be slow -- requiring a nested for loop over all line segments. </p> <p>Here's how to do it without a for loop (it's quite fast):</p> <pre><code>from numpy import where, dstack, diff, meshgrid def find_intersections(A, B): # min, max and all for arrays amin = lambda x1, x2: where(x1&lt;x2, x1, x2) amax = lambda x1, x2: where(x1&gt;x2, x1, x2) aall = lambda abools: dstack(abools).all(axis=2) slope = lambda line: (lambda d: d[:,1]/d[:,0])(diff(line, axis=0)) x11, x21 = meshgrid(A[:-1, 0], B[:-1, 0]) x12, x22 = meshgrid(A[1:, 0], B[1:, 0]) y11, y21 = meshgrid(A[:-1, 1], B[:-1, 1]) y12, y22 = meshgrid(A[1:, 1], B[1:, 1]) m1, m2 = meshgrid(slope(A), slope(B)) m1inv, m2inv = 1/m1, 1/m2 yi = (m1*(x21-x11-m2inv*y21) + y11)/(1 - m1*m2inv) xi = (yi - y21)*m2inv + x21 xconds = (amin(x11, x12) &lt; xi, xi &lt;= amax(x11, x12), amin(x21, x22) &lt; xi, xi &lt;= amax(x21, x22) ) yconds = (amin(y11, y12) &lt; yi, yi &lt;= amax(y11, y12), amin(y21, y22) &lt; yi, yi &lt;= amax(y21, y22) ) return xi[aall(xconds)], yi[aall(yconds)] </code></pre> <p>Then to use it, provide two lines as arguments, where is arg is a 2 column matrix, each row corresponding to an (x, y) point: </p> <pre><code># example from matplotlib contour plots Acs = contour(...) Bsc = contour(...) # A and B are the two lines, each is a # two column matrix A = Acs.collections[0].get_paths()[0].vertices B = Bcs.collections[0].get_paths()[0].vertices # do it x, y = find_intersections(A, B) </code></pre> <p>have fun</p>
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    1. COThank for sharing your solution!!
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