Plotting A Square Wave Using Matplotlib, Numpy And Scipy


  • Square waves are period waveforms.


  • However, Square waves are non-sinusoidal. The transition between the peak values is instantaneous in a square wave.


  • The period of the square wave that is starting from a position like zero crossing the time it takes to return to the same position again.


  • The period of the square wave is also called the pulse width.


  • To draw a square wave using matplotlib, scipy and numpy following details are required
    • Frequency of the square wave - Say 10 Hz - That is 10 cycles per second


  • The sampling frequency - That is how many data points with which the square wave is being constructed - higher the data points smoother the square is.


  • Square waves have a duty cycle of 50%. That is, the percentage of the waveform that occurs above zero axes is 50% for a square wave.


  • By default the signal.square() function of scipy takes a duty value of 0.5.



from scipy import signal

import matplotlib.pyplot as plot

import numpy as np


# Sampling rate 1000 hz / second

t = np.linspace(0, 1, 1000, endpoint=True)


# Plot the square wave signal

plot.plot(t, signal.square(2 * np.pi * 5 * t))


# Give a title for the square wave plot

plot.title('Sqaure wave - 5 Hz sampled at 1000 Hz /second')


# Give x axis label for the square wave plot



# Give y axis label for the square wave plot



plot.grid(True, which='both')


# Provide x axis and line color

plot.axhline(y=0, color='k')


# Set the max and min values for y axis

plot.ylim(-2, 2)


# Display the square wave drawn


Square wave

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