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# Python NumPy rot90() Function Example

Python NumPy rot90() is an inbuilt function that is used for rotating the elements of an array by 90 degrees along a specified axis. The rot90() can be imported as import NumPy as np, and we can create multidimensional arrays and derive other mathematical statistics with the help of NumPy, which is a library in Python.

## Python NumPy rot90()

The rot90() function is used to rotate the array by 90 degrees in the plane specified by axes. The rotation direction is from the first towards a second axis. An array of two or more dimensions. The number of times an array is rotated by 90 degrees.

### Syntax

```numpy.rot90 (input_array, k = 1, axes = (0, 1))
```

### Parameters

1. Input_array: It depicts the n-dimensional array where rotation is to be performed.
2. k: It represents the number of times we wish to rotate array by 90 degrees.
3. axes: It depicts the plane along which we want to rotate the array.

### Return Value

It returns the rotated version of the input_array.

### Write a program to show the working of the rot90() function.

See the following code.

```import numpy as np

array = np.arange(12).reshape(3, 4)
print("Original array : \n", array)

# Rotating once
print("\nRotated array : \n", np.rot90(array))

# Rotating twice
print("\nRotated array : \n", np.rot90(array, 2))```

#### Output

```Original array :
[[ 0  1  2  3]
[ 4  5  6  7]
[ 8  9 10 11]]

Rotated array :
[[ 3  7 11]
[ 2  6 10]
[ 1  5  9]
[ 0  4  8]]

Rotated array :
[[11 10  9  8]
[ 7  6  5  4]
[ 3  2  1  0]]```

#### Explanation

In the above code, Function 1 was used to rotate the array in 90 degrees only one time.

Function 2 was used to rotate the array in 90 degrees two times.

See the second example.

```import numpy as np

m = np.arange(8).reshape((2, 2, 2))
print("Original Array\n")
print(m)
print("Rotated Array\n")
print(np.rot90(m, 1, (1, 2)))
```

#### Output

```Original Array

[[[0 1]
[2 3]]

[[4 5]
[6 7]]]
Rotated Array

[[[1 3]
[0 2]]

[[5 7]
[4 6]]]```

#### Explanation

In the above code, function rotated the input array along (1, 2) place only one time.

Note: The numpy.rot90() returns the view. Because a view shares memory with an original array, changing one value changes the other.

## Specify the number of times to rotate: k

Specifying the integer value for a second argument k rotates the array 90 degrees counterclockwise k times. See the following code.

```import numpy as np

m = np.arange(8).reshape((2, 2, 2))
print("Original Array\n")
print(m)
print("Rotated Array\n")
print(np.rot90(m, 10))

print("Rotated Array 2nd time\n")
print(np.rot90(m, 11))

print("Rotated Array 3rd time\n")
print(np.rot90(m, 21))```

#### Output

```Original Array

[[[0 1]
[2 3]]

[[4 5]
[6 7]]]
Rotated Array

[[[6 7]
[4 5]]

[[2 3]
[0 1]]]
Rotated Array 2nd time

[[[4 5]
[0 1]]

[[6 7]
[2 3]]]
Rotated Array 3rd time

[[[2 3]
[6 7]]

[[0 1]
[4 5]]]```

## Conclusion

NumPy rot90() function is used to rotate the array by 90 degrees in the plane specified by axes. The rotation direction is from the first towards the second axis.