|MATLAB Function Reference|
Define persistent variable
persistent X Y Z
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.
Persistent variables are cleared when the M-file is cleared from memory or when the M-file is changed. To keep an M-file in memory until MATLAB quits, use
If the persistent variable does not exist the first time you issue the
persistent statement, it is 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.
There is no function form of the persistent command (i.e., you cannot use parentheses and quote the variable names).