Add what's new/example for no broken streamlines

aragilar · aragilar · commit d190205bb897 · 2022-04-01T21:05:18.000+11:00
diff --git a/doc/users/next_whats_new/no_broken_streamlines.rst b/doc/users/next_whats_new/no_broken_streamlines.rst
@@ -0,0 +1,25 @@
+Add option to plt.streamplot to not break streamlines
+-----------------------------------------------------
+
+It is now possible to specify that streamplots have continuous, unbroken
+streamlines. Previously streamlines would end to limit the number of lines
+within a single grid cell. See the difference between the plots below:
+
+.. plot::
+
+    import matplotlib.pyplot as plt
+    import numpy as np
+
+    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**2 + V**2)
+
+    fig, (ax0, ax1) = plt.subplots(1, 2, sharex=True)
+
+    ax0.streamplot(X, Y, U, V, broken_streamlines=True)
+    ax0.set_title('broken_streamlines=True')
+
+    ax1.streamplot(X, Y, U, V, broken_streamlines=False)
+    ax1.set_title('broken_streamlines=False')
diff --git a/examples/images_contours_and_fields/plot_streamplot.py b/examples/images_contours_and_fields/plot_streamplot.py
@@ -11,6 +11,8 @@
 * Varying the line width along a streamline.
 * Controlling the starting points of streamlines.
 * Streamlines skipping masked regions and NaN values.
+* Unbroken streamlines even when exceeding the limit of lines within a single
+  grid cell.
 """
 import numpy as np
 import matplotlib.pyplot as plt
@@ -61,13 +63,17 @@
 U[:20, :20] = np.nan
 U = np.ma.array(U, mask=mask)
 
-ax4 = fig.add_subplot(gs[2:, :])
+ax4 = fig.add_subplot(gs[2, 0])
 ax4.streamplot(X, Y, U, V, color='r')
 ax4.set_title('Streamplot with Masking')
 
 ax4.imshow(~mask, extent=(-w, w, -w, w), alpha=0.5, cmap='gray', aspect='auto')
 ax4.set_aspect('equal')
 
+ax5 = fig.add_subplot(gs[2, 1])
+ax5.streamplot(X, Y, U, V, broken_streamlines=False)
+ax5.set_title('Streamplot with with unbroken streamlines')
+
 plt.tight_layout()
 plt.show()
 #############################################################################
diff --git a/lib/matplotlib/streamplot.py b/lib/matplotlib/streamplot.py
@@ -18,7 +18,8 @@
 def streamplot(axes, x, y, u, v, density=1, linewidth=None, color=None,
                cmap=None, norm=None, arrowsize=1, arrowstyle='-|>',
                minlength=0.1, transform=None, zorder=None, start_points=None,
-               maxlength=4.0, integration_direction='both', broken_streamlines=True):
+               maxlength=4.0, integration_direction='both',
+               broken_streamlines=True):
     """
     Draw streamlines of a vector flow.
 
