如何在 matplotlib 3D scatter plot 上切换点的开和关？

Question

SOLVED (see below)

On 2D matpotlib scatter plot I can turn on and off points by accessing _offsets property of scatter plot object and setting it's .mask attribute True/False for indexes of those points we want to show/hide like this:

import matplotlib
import matplotlib.pyplot as plt
from matplotlib.widgets import Button
import random


def TogglePoints(event, plot):
    plot._offsets.mask = [ [1, 1], [1, 1], [1, 1], [0, 0], [0, 0], [0, 0] ]
    plot.figure.canvas.draw()


x = [random.randint(-10, 10) for n in range(6)]
y = [random.randint(-10, 10) for n in range(6)]
ax = plt.axes()
sc = ax.scatter(x, y, marker='o', s=20, alpha=1)
ax_button = plt.axes([0.81, 0.01, 0.1, 0.05])
button= Button(ax_button, "Toggle")
button.on_clicked(lambda event: TogglePoints(event, sc))
plt.show()

When you click the "Toggle" button on the figure, points with indexes 0, 1, 2 will disappear. You can make them re-appear by setting _offsets.mask back to False and re-drawing plot. This is what I want to achieve with matplotlib 3D scatter plot.

Using _offsets.mask = [ [1, 1], [1, 1], [1, 1], [0, 0], [0, 0], [0, 0] ] on 3D scatter plot doesn't seem to work. Actually it alters type of underlying array from MaskedArray to numpy.ndarray for some reason (see: Numpy MaskedArray in matplotlib 3D scatter plot, turns into ndarray when called by PyQt5 button click ). I know that 3D scatter plots have _offsets3d property. However I don't know how I can use it to show/hide points on the plot. Or maybe there's some other way?

Does anyone know how I can do that?

Answer 1

Thanks to this post:

Get working alpha value of scatter points in mpl_toolkits.basemap.Basemap

I've found a workaround that serves my purpose. It concerns setting alpha values of points with set_facecolors() . So the working code now looks like this:

...
import pandas as pd #added

def TogglePointsOFF(event, plot):
    for n in range(3): # n = index of point
        fc_colors[n, 3] = 0 # 4th value is alpha
    plot.set_facecolors(fc_colors)
    plot.figure.canvas.draw()

def TogglePointsON(event, plot):
    for n in range(3): # n = index of point
        fc_colors[n, 3] = 1 # 4th value is alpha
    plot.set_facecolors(fc_colors)
    plot.figure.canvas.draw()

#I've put it into DataFrame() so you can better see
df = pd.DataFrame()
df['label'] = ["data_"+str(n) for n in range(6)]
df['id'] = [1, 1, 1, 2, 2, 2]
['x'] = [random.randint(-10, 10) for n in range(6)]
['y'] = [random.randint(-10, 10) for n in range(6)]
['z'] = [random.randint(-10, 10) for n in range(6)]
colors = {1:'red', 2:'blue'} # to map colors with df 'id'

#plot points colored according to value of df['id']
ax = plt.axes()
sc = ax.scatter(df['x'], df['y'], df['z'], c=df['id'].map(colors), marker='o', s=20, depthshade=False)
global fc_colors #yeah yeah globals...
face_colors = sc._face_colors
ax_button = plt.axes([0.81, 0.01, 0.1, 0.05])
ax_button_1 = plt.axes([0.68, 0.01, 0.12, 0.05])
button= Button(ax_button, "OFF")
button_1= Button(ax_button_1, "ON")
button.on_clicked(lambda event: TogglePointsOFF(event, sc))
button_1.on_clicked(lambda event: TogglePointsON(event, sc))
plt.show()

Clicking buttons "ON" and "OFF" will hide/show group of points based on index.

I've tried using set_alpha() and passing iterable of alpha values like: [0, 0, 0, 1, 1, 1] however it seemed to work on random points and set alpha of incorrect points.

Also getting face_colors from get_facecolors() seemed to get colors with random index alignment. This may be connected why passing iterable with alpha values to set_alpha() didn't work. That's why I take colors of points from: sc._face_colors .

Thank you for your time.