Cmap带线图。可以在线下（但是实线）或渐变（但在线上）绘图

Question

我正在尝试基于使用pandas和matplotlib处理的数据集的可视化问题。我将数据绘制成线图。我的目标是让曲线下面的区域用cmap进行渐变（ex＆＃39; plasma＆＃39;）

然而，出于不同的原因，我最好的尝试都是错误的。第一个将使用渐变颜色，但仅限于线条。第二个将在线下着色，但只有纯色。我被困了很长时间......谢谢你！

ax = plot_chance_death.plot(kind='line', x = 'State', y = 'Percent Chance', 
ax=ax, color='indigo')
l1 = ax.lines[0]
x1 = l1.get_ydata()
y1 = l1.get_xdata()
fig, ax = plt.subplots()

# plot only the outline of the polygon, and capture the result
poly, = ax.fill(x1, y1, facecolor='none')

# get the extent of the axes
xmin, xmax = ax.get_xlim()
ymin, ymax = ax.get_ylim()

# create a dummy image
img_data = np.arange(ymin,ymax,(ymax-ymin)/100.)
img_data = img_data.reshape(img_data.size,1)

# plot and clip the image
im = ax.imshow(img_data, aspect='auto',  origin='upper', cmap='plasma', 
extent=[xmin,xmax,ymin,ymax], vmin=1., vmax=y1.max())

#this shows the gradient but above the line
im.set_clip_path(poly)

###this solution colors underneath but solid color
ax.fill_between(x1, y1, y2=0, cmap='plasma',  norm=(0,.5))

Answer 1

在Path中包含要用作clip_path的区域底部是有意义的。您可以从Path数据创建plot，然后将两个底部点添加到其中。

import pandas as pd
import numpy as np; np.random.seed(42)
import matplotlib.pyplot as plt
from matplotlib.path import Path

df = pd.DataFrame({"x" : np.linspace(0,0.05,40),
                   "y" : np.cumsum(np.random.rand(40))[::-1]*3})


fig, ax = plt.subplots()


l, = ax.plot(df.x, df.y, color="k")

# get the extent of the axes
xmin, xmax = ax.get_xlim()
ymin, ymax = ax.get_ylim()

# create a dummy image
img_data = np.arange(ymin,ymax,(ymax-ymin)/100.)
img_data = img_data.reshape(img_data.size,1)

# plot and clip the image
im = ax.imshow(img_data, aspect='auto',  origin='upper', cmap='plasma', 
               extent=[xmin,xmax,ymin,ymax], vmin=1., vmax=df.y.max())

px,py = l.get_data()

p0 = [[px[-1], py.min()], [px[0], py.min()]]
p = np.concatenate((np.c_[px,py],p0))
path = Path(p)

im.set_clip_path(path, transform=ax.transData)

plt.show()