Error in running the code

I have a code below for lsb replacement hiding text in image ,while running i ger error as

Undefined function or method 'fun' for input arguments of type 'uint8'.

Error in ==> lsbmr_grey at 146
            y=fun(xi,yi);           % calling function
code is

http://www.sendspace.com/file/euv8hg

please assis

[Sabarinathan Vadivelu]

y=fun(xi,yi);

I cant find this line in the code u referred