How to Create Histogram Using NumPy

Renesh Bedre    2 minute read

A histogram is useful for visualizing the frequency distribution of data as a bar graph. The height of the bar in the histogram represents the frequency counts of observations falling into each interval (bins).

In this article, you will learn how to create the histogram using the numpy.histogram() function from Python NumPy package.

The general syntax of numpy.histogram() looks like this:

# import package
import numpy as np

# generate random numbers
np.histogram(data, bins=10)

Where,

Parameter Description
data Input data in array format
bins number of equal-width bins. It can be single int value or sequence of values (default is 10)

The following examples explains how to use the numpy.histogram() function to generate histogram in Python.

Example 1: Generate default histogram

The following example shows how to generate a histogram using a numpy.histogram().

By default, the numpy.histogram() function generates 10 intervals for the histogram

# import package
import numpy as np

# generate random data
data = np.random.uniform(low=1, high=100, size=100)

# create numpy histogram with 10 intervals
hist, bins = np.histogram(data)
print(hist, bins)

# output
[ 7  9  7 10  8  9 15 15 10 10] 
[ 3.01807371 12.68467772 22.35128173 32.01788575 41.68448976 51.35109377
 61.01769778 70.6843018  80.35090581 90.01750982 99.68411384]

In the above output, the first array is frequency counts for each bin (equally-spaced intervals) and second array is the edges of the bins.

Now, plot the histogram,

# import package
import matplotlib.pyplot as plt

# draw histogram
plt.hist(data, bins=bins)
plt.xlabel("Bins (Intervals)")
plt.ylabel("Frequency counts")
plt.show()

Numpy histogram

Example 2: Generate histogram with specific bins

The following example shows how to generate a histogram with specific bins (intervals) using a numpy.histogram() function.

# import package
import numpy as np

# generate random data
data = np.random.uniform(low=1, high=100, size=100)

# create numpy histogram with 10 specific intervals
hist, bins = np.histogram(data, bins=[1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100])
print(hist, bins)

# output
[ 7  9  8 18  6 13  9  8 10 12]
[  1  10  20  30  40  50  60  70  80  90 100]

In the above output, the first array is frequency counts for each bin (equally-spaced interval) and the second array is the edges of the bins.

Now, plot the histogram,

# import package
import matplotlib.pyplot as plt

# draw histogram
plt.hist(data, bins=bins)
plt.xlabel("Bins (Intervals)")
plt.ylabel("Frequency counts")
plt.show()

Numpy histogram

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