Perm inv

perm_inv
Computes the inverse of a permutation
Other toolboxes required	none
Related functions	perm_sign
Function category	Helper functions

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.

1. %%  PERM_INV    Computes the inverse of a permutation

2. %   This function has one required argument:

3. %     PERM: a permutation vector

4. %

5. %   PI = perm_inv(PERM) is the inverse permutation of PERM.

6. %

7. %   URL: http://www.qetlab.com/perm_inv

9. %   requires: nothing

10. %   author: Nathaniel Johnston (nathaniel@njohnston.ca)

11. %   package: QETLAB

12. %   last updated: November 28, 2012

14. function res = perm_inv(perm)

16. [~,res] = sort(perm);