# numpy.diff() in Python with examples

This tutorial will help you learn about how to use **numpy.diff()** in Python.

`n`

** umpy.diff()** is one of the most widely used functions in Python and basically,

**it is used to calculate the difference between two consecutive values of a NumPy array**. The output of the function

**comes out in the form of**

`numpy.diff()`

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

. ## Example 1:

This is a very basic example to understand the **numpy.diff()** function.

# import the library import numpy as np # create the array array=np.array([4,2,5,3,9,1,7,0,9]) # difference between two consecutive elements of this array # out[i]=arr[i+1]-arr[i] new_array=np.diff(array) # print the new array print(new_array)

Output:

[-2 3 -2 6 -8 6 -7 9]

In this example, we can clearly see that the difference between all the consecutive values of this array is given in the output section of this Python program. This is also known as the **first order difference.**

## Example 2:

Now, if you want to calculate the difference between the consecutive values of a NumPy array multiple times, i.e… to calculate the difference between the consecutive values of the array made from the output of the first order difference. In this case, the first order difference array is **[-2 3 -2 6 -8 6 -7 9].**

**Second order difference:**

# import the library import numpy as np # create the array array=np.array([4,2,5,3,9,1,7,0,9]) print("Original Array",array) # difference between two consecutive elements of this array # out[i]=arr[i+1]-arr[i] First_order=np.diff(array) print("First order difference: ",First_order) # Second order difference new_array=np.diff(array,n=2) # print the new array print("Second order difference: ",new_array)

Output:

Original Array [4 2 5 3 9 1 7 0 9] First order difference: [-2 3 -2 6 -8 6 -7 9] Second order difference: [ 5 -5 8 -14 14 -13 16]

**Third order difference:**

# import the library import numpy as np # create the array array=np.array([4,2,5,3,9,1,7,0,9]) print("Original Array",array) # difference between two consecutive elements of this array # out[i]=arr[i+1]-arr[i] First_order=np.diff(array) print("First order difference: ",First_order) # Second order difference new_array=np.diff(array,n=2) # print the new array print("Second order difference: ",new_array) # Third order difference print("Third order difference: ",np.diff(array,n=3))

Output:

Original Array [4 2 5 3 9 1 7 0 9] First order difference: [-2 3 -2 6 -8 6 -7 9] Second order difference: [ 5 -5 8 -14 14 -13 16] Third order difference: [-10 13 -22 28 -27 29]

## Example 3:

We can also calculate the difference between the elements of a 2-dimensional NumPy array using the code below.

# Import the library import numpy as np # create the array array=np.array([[4,3,5,2,6],[2,1,8,9,4]]) # difference between the elements difference=np.diff(array,axis=0) # print the difference array print(difference)

Output:

[[-2 -2 3 7 -2]]

**Difference between the elements of the sub-arrays:**

# Import the library import numpy as np # create the array array=np.array([[4,3,5,2,6],[2,1,8,9,4]]) # difference between the elements of the sub-array difference=np.diff(array,axis=1) # print the difference array print(difference)

Output:

[[-1 2 -3 4] [-1 7 1 -5]]

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