Matplotlib plt.plot与枚举不起作用

Question

import numpy as np 
import matplotlib.pyplot as plt 

array = np.array([[1,2,3,4,5,6],[10,20,30,40,50,60],[3,4,5,6,7,8],[100,200,300,400,500,600]])

def plot(list):
    fig = plt.figure()
    ax = fig.add_subplot(111)

    for a,i in enumerate(list.T):
        ax.scatter(i[0],i[1],c='red') # This is plotted
        ax.plot(i[2],i[3],'g--') # THIS IS NOT BEING PLOTTED !!!! 
    fig.show()

plot(array)

Now, I need to call plot several times using different array lists. So my for loop cannot be removed. Is there any other way to plot a dotted line apart from calling plt.plot instead ?

This is the plot I get:

As you can see, I am not getting the plt.plot(i[2],i[3],'g--') . Why is this so ?

But when you print the values using the same for loop:

In [21]: for a,i in enumerate(array.T):
    ...:     print i[2],i[3]
    ...:     
3 100
4 200
5 300
6 400
7 500
8 600

The values are perfectly printed. They however are not plotted.

Answer 1

Remove the for loop:

ax.scatter(array[0],array[1],c='red')
ax.plot(array[0],array[1],'g--')

The problem with your code is that you iterate over rows, which is fine for plotting single dots ( ax.scatter ), but not for connecting single dots ( ax.plot with '--' option): at each row you only plot the line between that point and itself, which obviously doesn't show up in the graph.