WHICHDIR is the jCommon module of jLab.

    WHICHDIR  Returns directory name containing file in search path.
 
    WHICHDIR NAME returns the directory containing a file called NAME,
    i.e. the full path of the file excluding NAME and the trailing '/'. 
 
    If more than one directory contains a file called NAME, then 
    WHICHDIR returns a cell array of directories names.
 
    If NAME does not include an extension, then it is interpreted as
    the name of an m-file, i.e. having extension '.m' .
    _________________________________________________________________
    This is part of JLAB --- type 'help jlab' for more information 
    (C) 2006--2015 J.M. Lilly --- type 'help jlab_license' for details