基本散点图 plot，对角线上有参考数据（身份线）

Question

I have two arrays x,y obtained from a machine learning calculations and I wish to make a scatter plot with the reference data x on the diagonal in a way to visualize better the predicted values y against the true ones x. Please can you suggest me how to do it in python or gnuplot?

Answer 1

import numpy as np
import matplotlib.pyplot as plt

N = 50
x = np.random.rand(N)
y = np.random.rand(N)

colors = np.random.rand(N)

plt.scatter(x, y, c=colors)
plt.plot( [0,1],[0,1] )
plt.savefig('a.png')

This will produce:

Check this page for more information.

Answer 2

a simple example:

import matplotlib.pyplot as plt
import numpy as np

x=np.linspace(0,100,101) 
y=np.random.normal(x)    # add some noise

plt.plot(x,y,'r.') # x vs y
plt.plot(x,x,'k-') # identity line

plt.xlim(0,100)
plt.ylim(0,100)
plt.show()

Answer 3

In matplotlib, you can also draw an "infinite" line in order to avoid having to define the exact coordinates. For example, if you have an axes ax , you can do:

pt = (0, 0)
ax.axline(pt, slope=1, color='black')

where pt is an intersection point. Note if pt isn't included in the limits of the plot, the limits will be modified to include it.