How to put the Origin at the center of the cos curve in a figure in Python Matplotlib?

To put the Origin at the center of the cos curve in a figure, we can manipulate the spine positions in Matplotlib. This creates a mathematical coordinate system where both x and y axes intersect at the origin (0, 0).

Steps to Center the Origin

• Set the figure size and adjust the padding between and around the subplots.

• Create x and y data points using numpy.

• Set the position of the axes using spines, top, left, right and bottom.

• Plot x and y data points using plot() method.

• Set the title of the plot.

• To display the figure, use show() method.

Example

Here's how to center the origin for a cosine curve ?

import numpy as np
from matplotlib import pyplot as plt

plt.rcParams["figure.figsize"] = [7.50, 3.50]
plt.rcParams["figure.autolayout"] = True

x = np.linspace(-5, 5, 100)
y = np.cos(x)

ax = plt.gca()
ax.spines['top'].set_color('none')
ax.spines['left'].set_position('zero')
ax.spines['right'].set_color('none')
ax.spines['bottom'].set_position('zero')

plt.plot(x, y)
plt.title("$\bf{y=cos(x)}$")

plt.show()

How It Works

The key is manipulating the spine positions:

• ax.spines['left'].set_position('zero') − Moves the y-axis to x=0

• ax.spines['bottom'].set_position('zero') − Moves the x-axis to y=0

• ax.spines['top'].set_color('none') − Hides the top border

• ax.spines['right'].set_color('none') − Hides the right border

Alternative Method with Grid

You can also add a grid to make the coordinate system more visible ?

import numpy as np
from matplotlib import pyplot as plt

plt.rcParams["figure.figsize"] = [8.00, 4.00]
plt.rcParams["figure.autolayout"] = True

x = np.linspace(-2*np.pi, 2*np.pi, 100)
y = np.cos(x)

fig, ax = plt.subplots()

# Center the spines
ax.spines['left'].set_position('zero')
ax.spines['bottom'].set_position('zero')
ax.spines['right'].set_color('none')
ax.spines['top'].set_color('none')

# Add grid
ax.grid(True, alpha=0.3)

plt.plot(x, y, 'b-', linewidth=2, label='cos(x)')
plt.title("Cosine Curve with Centered Origin")
plt.xlabel('x')
plt.ylabel('y')

plt.show()

Conclusion

Use set_position('zero') on the left and bottom spines to center the origin. Hide unnecessary spines with set_color('none') for a clean mathematical plot appearance.