Matlab newbie - what is wrong with this script?

I am just learning Matlab so go easy on me. Trying to figure out what is wrong with this script specifically under the "if" statement is where I seem to be having the most problems.

 NUM=0;
 for i=1:13
    img(:,:,i)=read_LUM2;

    if exist('Left','var')==0; {
            Left=img;
            Left(Left<400)=0;
            Left(Left~=0)=1;
            Left=logical(Left);
            NUM=NUM+1;
            L(NUM)=mean2(img(Left));
            }
    else {
            Right=img;
            Right(Right<400)=0;
            Right(Right~=0)=1;
            Right=logical(Right);
            NUM=NUM+1;
            R(NUM)=mean2(img(Right));
            }
    end

 end
 L=L(1:13)';
 R=R(1:13)';

any help you can provide will be much appreciated!

Thanks!

[Azzi Abdelmalek]

What is the error message?

Answer 1

[per isakson]

Remove the curly braces "{}" and try again.

Answer 2

[Alex]

Thanks per isakson! That worked!