使用matplotlib基于某个变量用颜色绘制多个段

Question

根据Matplotlib: Plotting numerous disconnected line segments with different colors和matplotlib: how to change data points color based on some variable这两个主题的答案，我试图绘制一个列表给出的一组段，例如：

data = [(-118, -118), (34.07, 34.16),
        (-117.99, -118.15), (34.07, 34.16),
        (-118, -117.98), (34.16, 34.07)]

我想用基于第二个列表的颜色绘制每个段：

color_param = [9, 2, 21]

带有色彩图。到目前为止，我使用此行显示段：

plt.plot(*data)

我期待像

这样的东西

plt.plot(*data, c=color_param, cmap='hot')

会起作用，但事实并非如此。任何人都可以帮我解决这个问题吗？如果可能的话，我宁愿使用matplotlib。

提前谢谢！

Answer 1

您可以使用LineCollection，这是一个示例：

import pylab as pl
import numpy as np
from matplotlib.collections import LineCollection
x = np.linspace(0, 2*np.pi, 100)
y = np.sin(x)
c = np.cos(x)
lines = np.c_[x[:-1], y[:-1], x[1:], y[1:]]
lc = LineCollection(lines.reshape(-1, 2, 2), array=c, linewidths=3)
fig, ax = pl.subplots()
ax.add_collection(lc)
ax.set_xlim(x.min(), x.max())
ax.set_ylim(y.min(), y.max())
fig.show()

Answer 2

您可以考虑以下事项：

import numpy as np 
import pylab as pl 

# normalize this
color_param = np.array([9.0, 2.0, 21.0])
color_param = (color_param - color_param.min())/(color_param.max() - color_param.min())

data = [(-118, -118), (34.07, 34.16),
        (-117.99, -118.15), (34.07, 34.16),
        (-118, -117.98), (34.16, 34.07)]

startD = data[::2]
stopD  = data[1::2]



for start, stop, col in zip( startD, stopD,  color_param):
    pl.plot( start, stop, color = pl.cm.jet(col) )

pl.show()

记得色彩图pl.cm.hot(0.7)在显示0到1之间的数字时会返回一个颜色值。有时会非常方便，就像你的情况一样

编辑：

对于红色到绿色的色彩映射：

import pylab as pl 
import matplotlib.colors as col
import numpy as np 

cdict = {'red':   [(0.0,  1.0, 1.0),
                   (1.0,  0.0, 0.0)],
         'green':  [(0.0,  0.0, 0.0),
                   (1.0,  1.0, 1.0)],
         'blue':   [(0.0,  0.0, 0.0),
                    (1.0,  0.0, 0.0)]}

my_cmap = col.LinearSegmentedColormap('my_colormap',cdict,256)


for theta in np.linspace(0, np.pi*2, 30):
    pl.plot([0,np.cos(theta)], [0,np.sin(theta)], color=my_cmap(theta/(2*np.pi)) )

pl.show()