Question

I have these data structures:

  X axis values:
 delta_Array = np.array([1000,2000,3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000])

  Y Axis values
   error_matrix = 
 [[ 24.22468454  24.22570421  24.22589308  24.22595919  24.22598979
    24.22600641  24.22601644  24.22602294  24.2260274   24.22603059]
  [ 28.54275713  28.54503017  28.54545119  28.54559855  28.54566676
    28.54570381  28.54572615  28.54574065  28.5457506   28.54575771]]

How do I plot them as a line plot using matplotlib and python

This code I came up with renders a flat line as follows
figure(3)
i = 0

 for i in range(error_matrix.shape[0]):
  plot(delta_Array, error_matrix[i,:])

 title('errors')
 xlabel('deltas')
 ylabel('errors')
 grid()
 show()

The problem here looks like is scaling of the axes. But im not sure how to fix it. Any ideas, suggestions how to get the curvature showing up properly?

Answer 1

You could use ax.twinx to create twin axes:

import matplotlib.pyplot as plt
import numpy as np

delta_Array = np.array([1000,2000,3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000])

error_matrix = np.array(
    [[ 24.22468454, 24.22570421, 24.22589308, 24.22595919, 24.22598979, 24.22600641, 24.22601644, 24.22602294, 24.2260274, 24.22603059],
     [ 28.54275713, 28.54503017, 28.54545119, 28.54559855, 28.54566676, 28.54570381, 28.54572615, 28.54574065, 28.5457506, 28.54575771]])


fig = plt.figure()
ax = []
ax.append(fig.add_subplot(1, 1, 1))
ax.append(ax[0].twinx())
colors = ('red', 'blue')

for i,c in zip(range(error_matrix.shape[0]), colors):
    ax[i].plot(delta_Array, error_matrix[i,:], color = c)
plt.show()

yields

The red line corresponds to error_matrix[0, :], the blue with error_matrix[1, :].

Another possibility is to plot the ratio error_matrix[0, :]/error_matrix[1, :].