# numpy.diff() in Python

`numpy.diff(arr[, n[, axis]])` function is used when we calculate the n-th order discrete difference along the given axis. The first order difference is given by out[i] = arr[i+1] – arr[i] along the given axis. If we have to calculate higher differences, we are using diff recursively.

Synatx: numpy.diff()

Parameters:
arr : [array_like] Input array.
n : [int, optional] The number of times values are differenced.
axis : [int, optional] The axis along which the difference is taken, default is the last axis.

Returns : [ndarray]The n-th discrete difference. The output is the same as a except along axis where the dimension is smaller by n.

Code #1 :

 `# Python program explaining ` `# numpy.diff() method ` ` `  `   `  `# importing numpy ` `import` `numpy as geek  ` ` `  `# input array ` `arr ``=` `geek.array([``1``, ``3``, ``4``, ``7``, ``9``]) ` `  `  `print``(``"Input array  : "``, arr) ` `print``(``"First order difference  : "``, geek.diff(arr)) ` `print``(``"Second order difference : "``, geek.diff(arr, n ``=` `2``)) ` `print``(``"Third order difference  : "``, geek.diff(arr, n ``=` `3``)) `

Output:

```Input array  :  [1 3 4 7 9]
First order difference  :  [2 1 3 2]
Second order difference :  [-1  2 -1]
Third order difference  :  [ 3 -3]
```

Code #2 :

 `# Python program explaining ` `# numpy.diff() method ` ` `  `   `  `# importing numpy ` `import` `numpy as geek  ` ` `  `# input array ` `arr ``=` `geek.array([[``1``, ``2``, ``3``, ``5``], [``4``, ``6``, ``7``, ``9``]]) ` `  `  `print``(``"Input array  : "``, arr) ` `print``(``"Difference when axis is 0 : "``, geek.diff(arr, axis ``=` `0``)) ` `print``(``"Difference when axis is 1 : "``, geek.diff(arr, axis ``=` `1``)) `

Output:

```Input array  :  [[1 2 3 5]
[4 6 7 9]]
Difference with axis 0 :  [[3 4 4 4]]
Difference with axis 1 :  [[1 1 2]
[2 1 2]]
```

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