# Find Difference Between Numbers In Array Using np.diff — pythonpip.com

This tutorial help to find the differences between numbers in an array by `np.diff()` method. You can compare two or more array using this method.

# Python np.diff()

The NumPy array method `np.diff()` finds the differences between numbers in an array. The `np.diff()` function can be used to compare two or more arrays. If only one array is provided, the difference is calculated using `res[i] = arr[i+1] - arr[i]`.

# Syntax

`numpy.diff(a, n = 1, axis= -1, prepend = < no value >, append = < no value >)`

# Arguments

• a: This is the source array for which the difference is found using the `np.diff()` function.
• n: The number of times the array is differenced is passed as the argument to `n`. This is by default set to 1.
• axis: It is used to calculate the difference. It signifies that left to right is from right to left. The value is set to -1 by default. The axis can, however, be set to 0.
• prepend: The values appended at the beginning before performing the diff() function.
• append: The values that are appended at the ending before performing the diff() function.

# Return Value

The function np.diff() returns an array. This array contains values that represent the difference between two array integers.

Let’s takes some examples to understand np.diff() method fucntionality:

# Finding the difference in a single array using np.diff()

import numpy as np

arr = np.array([12, 10, 45, 65, 3])

diff_arr = np.diff(arr)
print(diff_arr)

## Output:

`[ -2 35 20 -62] ** Process exited - Return Code: 0 ** Press Enter to exit terminal`

We have imported numpy packages at the top of the file, created a new array and passed this array to `np.diff()` function.

The formula to calculate array number difference:

`diff_arr[i] = arr[i+1] - arr[i]`

As we can see the first index of the output array is store -2, that the difference between two array number( 10–12).

The outpot have :

`-2 = 10-12 35 = 45-10 20 = 65-45 -62 = 3-65`

# Finding the difference in a Multiple array using np.diff()

We’ll subtract the first array elements from the second array elements.

`# Importing numpy as np import numpy as np # array arr = np.array([[12, 10, 45, 65, 3], [45, 16, 35, 25, 83]]) # creating a new array diff_arr = np.diff(arr, n=1, axis=0) print(diff_arr)`

Output:

`[[ 33 6 -10 -40 80]] ** Process exited - Return Code: 0 ** Press Enter to exit terminal`

We have imported NumPy packages at the top of the file, created two new arrays and passed this array to `np.diff()` function.

The formula to calculate array number difference:

`diff_arr[0][i] = arr[1][i]-arr[0][i]`

As we can see the first index of the output array is store -2, which is the difference between two array number ( 10–12).

The output has:

`33 = 45-12 ... ...`

Originally published at https://www.pythonpip.com on May 16, 2022.

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