The working of perms

I tried perms('abc'). The doc says it is permutations in reverse lexicographic order. So I expected from the bottom - abc, acb, bac, bca so on. But the result I got was acb, abc, bac, bca ..... Can any one explain what is going on?

Answer 1

[Thorsten]

Have a look at

 perms(1:3)

The result you get with perms('abc') is analogous to this. To have lexicographic order, use

 sortrows(perms('abc'))

[Guillaume]

But the OP is correct. The doc is wrong and the order returned by perms is not reverse lexicograph.

For what it's worth, I've reported it to mathworks.

... and it's now been acknowledged as a bug.

[Seetha Rama Raju Sanapala]

@Guillaume. Thank you.

Answer 2

[Jan]

With Matlab R2011b I get:

perms('abc')

 cba
 cab
 bca
 bac
 abc
 acb

As reversed alphabetical order, I'd expect the last two lines to be swapped.

An efficient method to create the permutations in a sorted order: FEX: VChooseKO. But here the order is not "alphabetically" accoring to the contents of the input, but to the order of the values. So for an alphabetical order you'd need:

Str = 'acb';
VChooseKO(sort(Str), length(Str))