将点添加到现有的 matplotlib 散点图

Question

如何向现有图表添加点？直接的解决方案是绘制新的散点图，添加新数据。

ax.scatter(data[:,0], data[:,1], cmap = cmap, c = color_data)
ax.scatter(new_points_x, new_points_y, color='blue')

但是如果我们想用新的颜色添加更多的点，就有一个问题：我们必须考虑所有以前添加的点。

如果我可以使用像这样的特殊功能，那就太好了

AddPoint(ax, new_point, color)

我只想添加新颜色的新点。我不需要任何动画

Answer 1

It's unclear why creating a second scatter, as suggested by @b-fg, is not acceptable, but you could write a function like so:

def addPoint(scat, new_point, c='k'):
    old_off = scat.get_offsets()
    new_off = np.concatenate([old_off,np.array(new_point, ndmin=2)])
    old_c = scat.get_facecolors()
    new_c = np.concatenate([old_c, np.array(matplotlib.colors.to_rgba(c), ndmin=2)])

    scat.set_offsets(new_off)
    scat.set_facecolors(new_c)

    scat.axes.figure.canvas.draw_idle()

which allows you to add a new point to an existing PathCollection.

example:

fig, ax = plt.subplots()
scat = ax.scatter([0,1,2],[3,4,5],cmap=matplotlib.cm.spring, c=[0,2,1])
fig.canvas.draw()  # if running all the code in the same cell, this is required for it to work, not sure why
addPoint(scat, [3,6], 'c')
addPoint(scat, [3.1,6.1], 'pink')
addPoint(scat, [3.2,6.2], 'r')
addPoint(scat, [3.3,6.3], 'xkcd:teal')
ax.set_xlim(-1,4)
ax.set_ylim(2,7)

Note that the function that I'm proposing is very basic and would need to be made much smarter depending on the use case. It is important to realize that the facecolors array in a PathCollection does not necessarily have the same number of elements as the number of points, so funny things can happen with colors if you try to add several points as once, or if the original points are all the same colors, etc...

Answer 2

要添加具有新颜色的新数据，确实再次调用scatter将添加具有指定颜色的新点：

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(10)
a = np.random.rand(10)
plt.scatter(x, a, c='blue')
b = np.random.rand(10)
plt.scatter(x, b, c='red')
plt.show()