如何使用matplotlib从列表中绘制多个点？

Question

我已经从文本文件中读取了3D点列表。列表如下所示：

content = ['2.449,14.651,-0.992,', '6.833,13.875,-1.021,', '8.133,17.431,-1.150,', '3.039,13.724,-0.999,', '16.835,9.456,-1.031,', '16.835,9.457,-1.031,', '15.388,5.893,-0.868,', '13.743,25.743,-1.394,', '14.691,24.988,-1.387,', '15.801,25.161,-1.463,', '14.668,23.056,-1.382,', '22.378,20.268,-1.457,', '21.121,17.041,-1.353,', '19.472,13.555,-1.192,', '22.498,20.115,-1.436,', '13.344,-33.672,-0.282,', '13.329,-33.835,-0.279,', '13.147,-30.690,-0.305,', '13.097,-28.407,-0.339,', '13.251,-28.643,-0.366,', '13.527,-25.067,-0.481,', '19.433,-33.137,-0.408,', '19.445,-29.501,-0.345,', '20.592,-28.004,-0.312,', '19.109,-26.512,-0.380,', '18.521,-24.155,-0.519,', '22.837,48.245,-2.201,', '23.269,50.129,-2.282,', '23.499,46.652,-2.297,', '23.814,48.646,-2.271,', '30.377,46.501,-2.214,', '29.869,44.479,-2.143,', '29.597,41.257,-2.018,', '28.134,40.291,-2.159,', '-40.932,-0.320,-1.390,', '-36.808,0.442,-1.382,', '-30.831,0.548,-1.288,', '-29.404,1.235,-1.300,', '-26.453,1.424,-1.261,', '-30.559,2.775,-1.249,', '-27.714,3.439,-1.201,']

我想在3D图上绘制所有点。到目前为止，我已经知道了：

#!/usr/bin/env python

import numpy as np
import matplotlib.pyplot as plt

with open("measurements.txt") as f:
    content = f.read().splitlines()
#print content

for value in content:
    x, y, z = value.split(',')

#print x, y, z 
fig = plt.figure()
ax = plt.axes(projection='3d')

ax.scatter(x, y, z)

fig.savefig('scatterplot.png')

它抛出一个错误：

  

回溯（最近一次通话最后一次）：文件“ plotting.py”，位于第11行          x，y，z = value.split（'，'）       ValueError：太多值无法解压缩

如何绘制这些点？谢谢您的帮助。

Answer 1

首先，您需要通过在文件中分散行，然后将它们传递给函数，将值放入相应的数组中。

content = ['2.449,14.651,-0.992,', '6.833,13.875,-1.021,', '8.133,17.431,-1.150,', '3.039,13.724,-0.999,', '16.835,9.456,-1.031,', '16.835,9.457,-1.031,', '15.388,5.893,-0.868,', '13.743,25.743,-1.394,', '14.691,24.988,-1.387,', '15.801,25.161,-1.463,', '14.668,23.056,-1.382,', '22.378,20.268,-1.457,', '21.121,17.041,-1.353,', '19.472,13.555,-1.192,', '22.498,20.115,-1.436,', '13.344,-33.672,-0.282,', '13.329,-33.835,-0.279,', '13.147,-30.690,-0.305,', '13.097,-28.407,-0.339,', '13.251,-28.643,-0.366,', '13.527,-25.067,-0.481,', '19.433,-33.137,-0.408,', '19.445,-29.501,-0.345,', '20.592,-28.004,-0.312,', '19.109,-26.512,-0.380,', '18.521,-24.155,-0.519,', '22.837,48.245,-2.201,', '23.269,50.129,-2.282,', '23.499,46.652,-2.297,', '23.814,48.646,-2.271,', '30.377,46.501,-2.214,', '29.869,44.479,-2.143,', '29.597,41.257,-2.018,', '28.134,40.291,-2.159,', '-40.932,-0.320,-1.390,', '-36.808,0.442,-1.382,', '-30.831,0.548,-1.288,', '-29.404,1.235,-1.300,', '-26.453,1.424,-1.261,', '-30.559,2.775,-1.249,', '-27.714,3.439,-1.201,']

import numpy as np
import matplotlib.pyplot as plt

#with open("measurements.txt") as f:
    #content = f.read().splitlines()
#print content

#for value in content:
#    x, y, z = value.split(',')

x = [float(i.split(',')[0]) for i in content]
y = [float(i.split(',')[1]) for i in content]
z = [float(i.split(',')[2]) for i in content]
#print(x, y, z)
fig = plt.figure()
ax = plt.axes(projection='3d')

ax.scatter(x, y, z)

fig.savefig('scatterplot.png')

输出

Answer 2

很明显！进行拆分时，有4个值

content = ['2.449,14.651,-0.992,', '6.833,13.875,-1.021,', '8.133,17.431,-1.150,', '3.039,13.724,-0.999,', '16.835,9.456,-1.031,', '16.835,9.457,-1.031,', '15.388,5.893,-0.868,', '13.743,25.743,-1.394,', '14.691,24.988,-1.387,', '15.801,25.161,-1.463,', '14.668,23.056,-1.382,', '22.378,20.268,-1.457,', '21.121,17.041,-1.353,', '19.472,13.555,-1.192,', '22.498,20.115,-1.436,', '13.344,-33.672,-0.282,', '13.329,-33.835,-0.279,', '13.147,-30.690,-0.305,', '13.097,-28.407,-0.339,', '13.251,-28.643,-0.366,', '13.527,-25.067,-0.481,', '19.433,-33.137,-0.408,', '19.445,-29.501,-0.345,', '20.592,-28.004,-0.312,', '19.109,-26.512,-0.380,', '18.521,-24.155,-0.519,', '22.837,48.245,-2.201,', '23.269,50.129,-2.282,', '23.499,46.652,-2.297,', '23.814,48.646,-2.271,', '30.377,46.501,-2.214,', '29.869,44.479,-2.143,', '29.597,41.257,-2.018,', '28.134,40.291,-2.159,', '-40.932,-0.320,-1.390,', '-36.808,0.442,-1.382,', '-30.831,0.548,-1.288,', '-29.404,1.235,-1.300,', '-26.453,1.424,-1.261,', '-30.559,2.775,-1.249,', '-27.714,3.439,-1.201,']

解决方案：

for value in content:
    x, y, z,parasitic_value = value.split(',')

Answer 3

content中的元素是：

'2.449,14.651,-0.992,'

从该字符串中提取要绘制的数据的方式略有不同，是将其视为元组，并使用eval()。

data = [eval("("+x[:len(x)-1]+")") for x in content]

哪个返回：

[(2.449, 14.651, -0.992),
 (6.833, 13.875, -1.021),
 (8.133, 17.431, -1.15),
 ...
 (-30.559, 2.775, -1.249),
 (-27.714, 3.439, -1.201)]

编辑：您得到的错误意味着：

您需要3个值，X，Y和Z；但是当我在","分家时，还有更多（要解包的值太多）。

content[0].split(",")
Out[4]: ['2.449', '14.651', '-0.992', '']

Answer 4

我在那里至少看到一个错误。

最明显的一个（因为出现错误）是拆分。 末尾的第三个逗号将字符串分成四个元素

>>> l = 'a,b,c,'
>>> l.split(',')
['a', 'b', 'c', '']

您可以使用以下方法解决此问题：

x,y,z,_ = value.split(',')

您遇到的下一个问题是循环

for value in content:
    x, y, z = value.split(',')

您只存储了最后一个值，因为您多次覆盖了它们。 解决此问题的最简单方法是创建三个列表并将其追加到其中：

x = []
y = []
z = []
for measurement in content:
    a,b,c,_ = measurement.split(',')
    x.append(a)
    y.append(b)
    z.append(c)

这不是最有效的方法，但我认为应该更容易理解。

我建议这样使用它：

x = []
y = []
z = []
with open('measurements.txt') as file:
    for line in file:
        a,b,c,_ = line.split(',')
        x.append(a)
        y.append(b)
        z.append(c)

Answer 5

要解决主要问题，您必须编辑列表，并通过复制所有值并通过re遍历列表，使其成为3d numpy数组。

与其假定列表为多个点，不如将前2个点或3个点作为图像/ 3D图形，然后使用imshow或Axes3D进行绘制。