How to draw axis in the middle of the figure?

Question

I want to draw a figure in matplotib where the axis are displayed within the plot itself not on the side

I have tried the following code from here:

import math import numpy as np import matplotlib.pyplot as plt  def sigmoid(x):     a = []     for item in x:         a.append(1/(1+math.exp(-item)))     return a  x = np.arange(-10., 10., 0.2) sig = sigmoid(x)  plt.plot(x,sig) plt.show() 

The above code displays the figure like this:

What I would like to draw is something as follows (image from Wikipedia)

This question describes a similar problem, but it draws a reference line in the middle but no axis.

Answer 1

One way to do it is using spines:

import math import numpy as np import matplotlib.pyplot as plt  def sigmoid(x):     a = []     for item in x:         a.append(1/(1+math.exp(-item)))     return a   x = np.arange(-10., 10., 0.2) sig = sigmoid(x)  fig = plt.figure() ax = fig.add_subplot(1, 1, 1)  # Move left y-axis and bottim x-axis to centre, passing through (0,0) ax.spines['left'].set_position('center') ax.spines['bottom'].set_position('center')  # Eliminate upper and right axes ax.spines['right'].set_color('none') ax.spines['top'].set_color('none')  # Show ticks in the left and lower axes only ax.xaxis.set_ticks_position('bottom') ax.yaxis.set_ticks_position('left')  plt.plot(x,sig) plt.show() 

shows: