# 填充线条之间的区域

import matplotlib.pyplot as plt
import numpy as np

x = np.arange(0.0, 2, 0.01)
y1 = np.sin(2 * np.pi * x)
y2 = 1.2 * np.sin(4 * np.pi * x)

fig, (ax1, ax2, ax3) = plt.subplots(3, 1, sharex=True)

ax1.fill_between(x, 0, y1)
ax1.set_ylabel('between y1 and 0')

ax2.fill_between(x, y1, 1)
ax2.set_ylabel('between y1 and 1')

ax3.fill_between(x, y1, y2)
ax3.set_ylabel('between y1 and y2')
ax3.set_xlabel('x')


fig, (ax, ax1) = plt.subplots(2, 1, sharex=True)
ax.plot(x, y1, x, y2, color='black')
ax.fill_between(x, y1, y2, where=y2 >= y1, facecolor='green', interpolate=True)
ax.fill_between(x, y1, y2, where=y2 <= y1, facecolor='red', interpolate=True)
ax.set_title('fill between where')

# Test support for masked arrays.
ax1.plot(x, y1, x, y2, color='black')
ax1.fill_between(x, y1, y2, where=y2 >= y1,
facecolor='green', interpolate=True)
ax1.fill_between(x, y1, y2, where=y2 <= y1,
facecolor='red', interpolate=True)
ax1.set_title('Now regions with y2>1 are masked')


fig, ax = plt.subplots()
y = np.sin(4 * np.pi * x)
ax.plot(x, y, color='black')

# use data coordinates for the x-axis and the axes coordinates for the y-axis
import matplotlib.transforms as mtransforms
trans = mtransforms.blended_transform_factory(ax.transData, ax.transAxes)
theta = 0.9
ax.axhline(theta, color='green', lw=2, alpha=0.5)
ax.axhline(-theta, color='red', lw=2, alpha=0.5)
ax.fill_between(x, 0, 1, where=y > theta,
facecolor='green', alpha=0.5, transform=trans)
ax.fill_between(x, 0, 1, where=y < -theta,
facecolor='red', alpha=0.5, transform=trans)

plt.show()