%PERSISTENT Define persistent variable.
%   PERSISTENT X Y Z defines X, Y, and Z as variables that are local 
%   to the function in which they are declared yet their values are 
%   retained in memory between calls to the function.  Persistent 
%   variables are similar to global variables because MATLAB creates 
%   permanent storage for both.  They differ from global variables in 
%   that persistent variables are known only to the function in which 
%   they are declared.  This prevents persistent variables from being 
%   changed by other functions or from the MATLAB command line.
%
%   Whenever you clear or modify a function that is in memory, MATLAB also
%   clears all persistent variables declared by that function. To keep a
%   function in memory until MATLAB quits, use MLOCK.
%
%   If the persistent variable does not exist the first time you issue
%   the PERSISTENT statement, it will be initialized to the empty matrix.
%
%   It is an error to declare a variable persistent if a variable with
%   the same name exists in the current workspace.
%
%   See also GLOBAL, CLEAR, CLEARVARS, MLOCK, MUNLOCK, MISLOCKED.

%   Copyright 1984-2015 The MathWorks, Inc.
%   Built-in function.
