Add example to plot streamplot with masked values.

tonysyu · tonysyu · commit a98c543e0eb2 · 2012-01-18T23:50:32.000-05:00
diff --git a/examples/pylab_examples/streamplot_with_mask.py b/examples/pylab_examples/streamplot_with_mask.py
@@ -0,0 +1,23 @@
+"""
+Demonstrate the use of the `streamplot` function using a masked array
+and NaN values.
+"""
+import numpy as np
+import matplotlib.pyplot as plt
+
+w = 3
+Y, X = np.mgrid[-w:w:100j, -w:w:100j]
+U = -1 - X**2 + Y
+V = 1 + X - Y**2
+speed = np.sqrt(U*U + V*V)
+
+mask = np.zeros(U.shape, dtype=bool)
+mask[40:60, 40:60] = 1
+U = np.ma.array(U, mask=mask)
+U[:20, :20] = np.nan
+
+plt.streamplot(X, Y, U, V, color='r')
+plt.imshow(~mask, extent=(-w, w, -w, w), alpha=0.5, interpolation='nearest')
+
+plt.show()
+
