# Perm inv

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perm_inv | |

Computes the inverse of a permutation | |

Other toolboxes required | none |
---|---|

Related functions | perm_sign |

Function category | Helper functions |

This is a helper function that only exists to aid other functions in QETLAB. If you are an end-user of QETLAB, you likely will never have a reason to use this function. |

` perm_inv` is a function that computes the inverse of a permutation.

## Syntax

`PI = perm_inv(PERM)`

## Argument descriptions

`PERM`: A vector containing a permutation of the integers 1, 2, ..., n.

## Examples

### Small examples

The identity permutation is its own inverse:

```
>> perm_inv(1:4)
ans =
1 2 3 4
```

To compute the inverse of the permutation on this MathWorld page, we can use the following line of code:

```
>> perm_inv([3,8,5,10,9,4,6,1,7,2])
ans =
8 10 1 6 3 7 9 2 5 4
```

## Source code

Click on "expand" to the right to view the MATLAB source code for this function.