matplotlib散点图颜色与第三个变量的函数 [英] matplotlib scatter plot colour as function of third variable
问题描述
我想知道如何通过第三个变量使matplotlib的散点函数色点.
I would like to know how to make matplotlib's scatter function colour points by a third variable.
问题 matplotlib中的gnuplot linecolor变量?和
Questions
gnuplot linecolor variable in matplotlib? and Matplotlib scatterplot; colour as a function of a third variable
posed similar queries, however, the answers to those questions don't address my issue: the use of c=arraywhichspecifiespointcolour
in the scatter function only sets the fill colour, not the edge colour. This means that the use of c=arr...
fails when using markersymbol='+'
, for instance (because that marker has no fill, only edges). I want points to be coloured by a third variable reliably, regardless of which symbol is used.
有没有一种方法可以通过Matplotlib的散点函数来实现?
Is there a way to achieve this with Matplotlib's scatter function?
推荐答案
这适用于我,使用matplotlib 1.1:
This works for me, using matplotlib 1.1:
import numpy as np
import matplotlib.pyplot as plt
x = np.arange(10)
y = np.sin(x)
plt.scatter(x, y, marker='+', s=150, linewidths=4, c=y, cmap=plt.cm.coolwarm)
plt.show()
结果:
或者,对于n个点,制作形状为(n,3)的RGB颜色值数组,并将其分配给scatter()
的edgecolors
关键字参数:
Alternatively, for n points, make an array of RGB color values with shape (n, 3), and assign it to the edgecolors
keyword argument of scatter()
:
import numpy as np
import matplotlib.pyplot as plt
x = np.linspace(0, 20, 100)
y = np.sin(x)
z = x + 20 * y
scaled_z = (z - z.min()) / z.ptp()
colors = plt.cm.coolwarm(scaled_z)
plt.scatter(x, y, marker='+', edgecolors=colors, s=150, linewidths=4)
plt.show()
结果:
该示例通过将z
值缩放到[0,1]范围并使用缩放后的值调用颜色映射plt.cm.coolwarm
来获取RGBA值.当以这种方式调用时,matplotlib颜色图将返回RGBA值的数组,每一行都给出相应输入值的颜色.例如:
That example gets the RGBA values by scaling the z
values to the range [0,1], and calling the colormap plt.cm.coolwarm
with the scaled values. When called this way, a matplotlib colormap returns an array of RGBA values, with each row giving the color of the corresponding input value. For example:
>>> t = np.linspace(0, 1, 5)
>>> t
array([ 0. , 0.25, 0.5 , 0.75, 1. ])
>>> plt.cm.coolwarm(t)
array([[ 0.2298, 0.2987, 0.7537, 1. ],
[ 0.5543, 0.6901, 0.9955, 1. ],
[ 0.8674, 0.8644, 0.8626, 1. ],
[ 0.9567, 0.598 , 0.4773, 1. ],
[ 0.7057, 0.0156, 0.1502, 1. ]])
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