How do I normalize values in NumPy array between 0 and 1?

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To normalize the values in a NumPy array to be between 0 and 1, you can use one of the following methods:

Method 1: Use NumPy

import numpy as np

x_norm = (x-np.min(x))/(np.max(x)-np.min(x))

Method 2: Use Sklearn

from sklearn import preprocessing as pre

x = x.reshape(-1, 1)

x_norm = pre.MinMaxScaler().fit_transform(x)

Both methods assume x is the name of the NumPy array you would like to normalize.

The following examples show how to use each method in practice.

Example 1: Normalize Values Using NumPy

Suppose we have the following NumPy array:

import numpy as np

#create NumPy array
x = np.array([13, 16, 19, 22, 23, 38, 47, 56, 58, 63, 65, 70, 71])

We can use the following code to normalize each value in the array to be between 0 and 1:

#normalize all values to be between 0 and 1
x_norm = (x-np.min(x))/(np.max(x)-np.min(x))

#view normalized array
print(x_norm)

[0.         0.05172414 0.10344828 0.15517241 0.17241379 0.43103448
 0.5862069  0.74137931 0.77586207 0.86206897 0.89655172 0.98275862
 1.        ]

Each value in the NumPy array has been normalized to be between 0 and 1.

Here’s how it worked:

The minimum value in the dataset is 13 and the maximum value is 71.

To normalize the first value of 13, we would apply the formula shared earlier:

• z_i = (x_i – min(x)) / (max(x) – min(x))  = (13 – 13) / (71 – 13) = 0

• z_i = (x_i – min(x)) / (max(x) – min(x)) = (16 – 13) / (71 – 13) = .0517

To normalize the third value of 19, we would use the same formula:

• z_i = (x_i – min(x)) / (max(x) – min(x)) = (19 – 13) / (71 – 13) = .1034

We use this same formula to normalize each value in the original NumPy array to be between 0 and 1.

Example 2: Normalize Values Using sklearn

Once again, suppose we have the following NumPy array:

import numpy as np

#create NumPy array
x = np.array([13, 16, 19, 22, 23, 38, 47, 56, 58, 63, 65, 70, 71])

We can use the MinMaxScaler() function from sklearn to normalize each value in the array to be between 0 and 1:

from sklearn import preprocessing as pre

#reshape array so that it works with sklearn
x = x.reshape(-1, 1)

#normalize all values to be between 0 and 1
x_norm = pre.MinMaxScaler().fit_transform(x)

#view normalized array
print(x_norm)

[[0.        ]
 [0.05172414]
 [0.10344828]
 [0.15517241]
 [0.17241379]
 [0.43103448]
 [0.5862069 ]
 [0.74137931]
 [0.77586207]
 [0.86206897]
 [0.89655172]
 [0.98275862]
 [1.        ]]

Each value in the NumPy array has been normalized to be between 0 and 1.

Notice that these normalized values match the ones calculated using the previous method.

The following tutorials explain how to perform other common tasks in NumPy: