Backport PR #11462: Doc: beautify usetex demo example

timhoffm · MeeseeksDev[bot] · commit 30788aa97b60 · 2018-06-20T22:40:46.000Z
diff --git a/examples/text_labels_and_annotations/usetex_demo.py b/examples/text_labels_and_annotations/usetex_demo.py
@@ -3,77 +3,67 @@
 Usetex Demo
 ===========
 
+Shows how to use latex in a plot.
+
+Also refer to the :doc:`/tutorials/text/usetex` guide.
 """
-import matplotlib
-matplotlib.rc('text', usetex=True)
-import matplotlib.pyplot as plt
+
 import numpy as np
+import matplotlib.pyplot as plt
+plt.rc('text', usetex=True)
 
 # interface tracking profiles
 N = 500
 delta = 0.6
 X = np.linspace(-1, 1, N)
 plt.plot(X, (1 - np.tanh(4 * X / delta)) / 2,    # phase field tanh profiles
-         X, (X + 1) / 2,                         # level set distance function
-         X, (1.4 + np.tanh(4 * X / delta)) / 4,  # composition profile
+         X, (1.4 + np.tanh(4 * X / delta)) / 4, "C2",  # composition profile
          X, X < 0, 'k--')                        # sharp interface
 
 # legend
-plt.legend(('phase field', 'level set', 'composition', 'sharp interface'),
-           shadow=True, loc=(0.01, 0.55))
-
-ltext = plt.gca().get_legend().get_texts()
-plt.setp(ltext[0], fontsize=20)
-plt.setp(ltext[1], fontsize=20)
-plt.setp(ltext[2], fontsize=20)
-plt.setp(ltext[3], fontsize=20)
+plt.legend(('phase field', 'level set', 'sharp interface'),
+           shadow=True, loc=(0.01, 0.48), handlelength=1.5, fontsize=16)
 
 # the arrow
-height = 0.1
-offset = 0.02
-plt.plot((-delta / 2., delta / 2), (height, height), 'k', linewidth=2)
-plt.plot((-delta / 2, -delta / 2 + offset * 2), (height, height - offset),
-         'k', linewidth=2)
-plt.plot((-delta / 2, -delta / 2 + offset * 2), (height, height + offset),
-         'k', linewidth=2)
-plt.plot((delta / 2, delta / 2 - offset * 2), (height, height - offset),
-         'k', linewidth=2)
-plt.plot((delta / 2, delta / 2 - offset * 2), (height, height + offset),
-         'k', linewidth=2)
-plt.text(-0.06, height - 0.06, r'$\delta$', {'color': 'k', 'fontsize': 24})
+plt.annotate("", xy=(-delta / 2., 0.1), xycoords='data',
+             xytext=(delta / 2., 0.1), textcoords='data',
+             arrowprops=dict(arrowstyle="<->", connectionstyle="arc3"))
+plt.text(0, 0.1, r'$\delta$',
+         {'color': 'k', 'fontsize': 24, 'ha' : 'center', 'va' : 'center',
+          'bbox' : dict(boxstyle="round", fc="w", ec="k", pad=0.2)})
 
-# X-axis label
-plt.xticks((-1, 0, 1), ('-1', '0', '1'), color='k', size=20)
+# Use tex in labels
+plt.xticks((-1, 0, 1), ('$-1$', r'$\pm 0$', '$+1$'), color='k', size=20)
 
-# Left Y-axis labels
-plt.ylabel(r'\bf{phase field} $\phi$', {'color': 'b', 'fontsize': 20})
-plt.yticks((0, 0.5, 1), ('0', '.5', '1'), color='k', size=20)
+# Left Y-axis labels, combine math mode and text mode
+plt.ylabel(r'\bf{phase field} $\phi$', {'color': 'C0', 'fontsize': 20})
+plt.yticks((0, 0.5, 1), (r'\bf{0}', r'\bf{.5}', r'\bf{1}'), color='k', size=20)
 
 # Right Y-axis labels
-plt.text(1.05, 0.5, r"\bf{level set} $\phi$", {'color': 'g', 'fontsize': 20},
+plt.text(1.02, 0.5, r"\bf{level set} $\phi$", {'color': 'C2', 'fontsize': 20},
          horizontalalignment='left',
          verticalalignment='center',
          rotation=90,
-         clip_on=False)
-plt.text(1.01, -0.02, "-1", {'color': 'k', 'fontsize': 20})
-plt.text(1.01, 0.98, "1", {'color': 'k', 'fontsize': 20})
-plt.text(1.01, 0.48, "0", {'color': 'k', 'fontsize': 20})
+         clip_on=False,
+         transform=plt.gca().transAxes)
 
+# Use multiline environment inside a `text`.
 # level set equations
-plt.text(0.1, 0.85,
-         r'$|\nabla\phi| = 1,$ \newline $ \frac{\partial \phi}{\partial t}'
-         r'+ U|\nabla \phi| = 0$',
-         {'color': 'g', 'fontsize': 20})
+eq1 = r"\begin{eqnarray*}" + \
+      r"|\nabla\phi| &=& 1,\\" + \
+      r"\frac{\partial \phi}{\partial t} + U|\nabla \phi| &=& 0 " + \
+      r"\end{eqnarray*}"
+plt.text(1, 0.9, eq1, {'color': 'C2', 'fontsize': 18}, va="top", ha="right")
 
 # phase field equations
-plt.text(0.2, 0.15,
-         r'$\mathcal{F} = \int f\left( \phi, c \right) dV,$ \newline '
-         r'$ \frac{ \partial \phi } { \partial t } = -M_{ \phi } '
-         r'\frac{ \delta \mathcal{F} } { \delta \phi }$',
-         {'color': 'b', 'fontsize': 20})
+eq2 = r'\begin{eqnarray*}' + \
+      r'\mathcal{F} &=& \int f\left( \phi, c \right) dV, \\ ' + \
+      r'\frac{ \partial \phi } { \partial t } &=& -M_{ \phi } ' + \
+      r'\frac{ \delta \mathcal{F} } { \delta \phi }' + \
+      r'\end{eqnarray*}'
+plt.text(0.18, 0.18, eq2, {'color': 'C0', 'fontsize': 16})
 
-# these went wrong in pdf in a previous version
-plt.text(-.9, .42, r'gamma: $\gamma$', {'color': 'r', 'fontsize': 20})
-plt.text(-.9, .36, r'Omega: $\Omega$', {'color': 'b', 'fontsize': 20})
+plt.text(-1, .30, r'gamma: $\gamma$', {'color': 'r', 'fontsize': 20})
+plt.text(-1, .18, r'Omega: $\Omega$', {'color': 'b', 'fontsize': 20})
 
 plt.show()
