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Fix example of streamplot start_points option #6672

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Merged
merged 3 commits into from
Jul 3, 2016
Merged

Fix example of streamplot start_points option #6672

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d2675d4
Fix docstring
afvincent Jul 1, 2016
6f5f347
Remove index on 'fig0' and 'ax0' (only ones of their kind)
afvincent Jul 1, 2016
baaadcf
Same vector field as other examples & more demonstrative seeds
afvincent Jul 1, 2016
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32 changes: 14 additions & 18 deletions examples/images_contours_and_fields/streamplot_demo_start_points.py
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Original file line number Diff line number Diff line change
@@ -1,30 +1,26 @@
"""
Demo of the `streamplot` function.
Demo of the streamplot function with starting points.

A streamplot, or streamline plot, is used to display 2D vector fields. This
example shows a few features of the stream plot function:

* Varying the color along a streamline.
* Varying the density of streamlines.
* Varying the line width along a stream line.
This example shows how to fix the streamlines that are plotted, by passing
an array of seed points to the `start_points` keyword argument.
"""
import numpy as np
import matplotlib.pyplot as plt

X, Y = (np.linspace(-3, 3, 100),
np.linspace(-3, 3, 100))

U, V = np.mgrid[-3:3:100j, 0:0:100j]
Y, X = np.mgrid[-3:3:100j, -3:3:100j]
U = -1 - X**2 + Y
V = 1 + X - Y**2

seed_points = np.array([[-2, 0, 1], [-2, 0, 1]])
# 5 points along the first diagonal and a point in the left upper quadrant
seed_points = np.array([[-2, -1, 0, 1, 2, -1], [-2, -1, 0, 1, 2, 2]])

fig0, ax0 = plt.subplots()
strm = ax0.streamplot(X, Y, U, V, color=U, linewidth=2,
cmap=plt.cm.autumn, start_points=seed_points.T)
fig0.colorbar(strm.lines)
fig, ax = plt.subplots()
strm = ax.streamplot(X, Y, U, V, color=U, linewidth=2,
cmap=plt.cm.autumn, start_points=seed_points.T)
fig.colorbar(strm.lines)

ax0.plot(seed_points[0], seed_points[1], 'bo')
ax.plot(seed_points[0], seed_points[1], 'bo')

ax0.axis((-3, 3, -3, 3))
ax.axis((-3, 3, -3, 3))

plt.show()