Andrey Popov

I'd prefer "mkdir(foldername)" instead of "eval(['mkdir ' folder_name])".
The "fclose('all')" is not helpful, if a file cannot be opened. There is also no reason to close all files in case of success, prefer "fclose(F)".
Under Linux (and as far as I can see under modern Matlab versions under Windows also) the file separators are CHAR(10). Therefore checking for 13 is not secure.
You use "ind" as loop index of two nested loops. Although this might works, it is recommended to avoid this.

This function does not work (and rightfully so!) when 1) the input is not square or when idp does not contain a permutation of all N numbers between 1 and N (for instance [1 3 3]). However, such likely inputs lead to unfriendly error messages, so I suggest you add some error checks in your code.
Furthermore, P can be defined more easily as
  P = eye(size(A)) ;
  P = P(idp,:) ;
Finally, the help section is quite nice, but lacks a description of the third output. And, btw, is the copyright really needed given the BSD license. So, room for improvement.