Difference between revisions of "Perm inv"
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(Created page with "{{Function |name=perm_inv |desc=Computes the inverse of a permutation |upd=November 28, 2012 |v=1.00 |helper=1}} <tt>'''perm_inv'''</tt> is a function th...") |
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|name=perm_inv | |name=perm_inv | ||
|desc=Computes the inverse of a permutation | |desc=Computes the inverse of a permutation | ||
| + | |rel=[[perm_sign]] | ||
| + | |cat=[[List of functions#Helper_functions|Helper functions]] | ||
|upd=November 28, 2012 | |upd=November 28, 2012 | ||
| − | |v= | + | |v=0.50 |
|helper=1}} | |helper=1}} | ||
<tt>'''perm_inv'''</tt> is a [[List of functions|function]] that computes the [http://mathworld.wolfram.com/InversePermutation.html inverse of a permutation]. | <tt>'''perm_inv'''</tt> is a [[List of functions|function]] that computes the [http://mathworld.wolfram.com/InversePermutation.html inverse of a permutation]. | ||
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===Small examples=== | ===Small examples=== | ||
The identity permutation is its own inverse: | The identity permutation is its own inverse: | ||
| − | < | + | <syntaxhighlight> |
>> perm_inv(1:4) | >> perm_inv(1:4) | ||
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1 2 3 4 | 1 2 3 4 | ||
| − | </ | + | </syntaxhighlight> |
To compute the inverse of the permutation on [http://mathworld.wolfram.com/InversePermutation.html this MathWorld page], we can use the following line of code: | To compute the inverse of the permutation on [http://mathworld.wolfram.com/InversePermutation.html this MathWorld page], we can use the following line of code: | ||
| − | < | + | <syntaxhighlight> |
>> perm_inv([3,8,5,10,9,4,6,1,7,2]) | >> perm_inv([3,8,5,10,9,4,6,1,7,2]) | ||
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8 10 1 6 3 7 9 2 5 4 | 8 10 1 6 3 7 9 2 5 4 | ||
| − | </ | + | </syntaxhighlight> |
| + | |||
| + | {{SourceCode|name=perm_inv|helper=1}} | ||
Latest revision as of 16:08, 29 September 2014
| 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 4To 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 4Source code
Click here to view this function's source code on github.