# rotm2axang

Convert rotation matrix to axis-angle rotation

## Syntax

``axang = rotm2axang(rotm)``

## Description

example

````axang = rotm2axang(rotm)` converts a rotation given as an orthonormal rotation matrix, `rotm`, to the corresponding axis-angle representation, `axang`. The input rotation matrix must be in the premultiply form for rotations.```

## Examples

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```rotm = [1 0 0 ; 0 -1 0; 0 0 -1]; axang = rotm2axang(rotm)```
```axang = 1×4 1.0000 0 0 3.1416 ```

## Input Arguments

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Rotation matrix, specified as a 3-by-3-by-n matrix containing n rotation matrices. Each rotation matrix has a size of 3-by-3 and must be orthonormal. The input rotation matrix must be in the premultiply form for rotations.

Note

Rotation matrices that are slightly non-orthonormal can give complex outputs. Consider validating your matrix before inputting to the function.

Example: `[0 0 1; 0 1 0; -1 0 0]`

## Output Arguments

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Rotation given in axis-angle form, returned as an n-by-4 matrix of n axis-angle rotations. The first three elements of every row specify the rotation axis, and the last element defines the rotation angle (in radians).

Example: `[1 0 0 pi/2]`

## Version History

Introduced in R2015a