Error: Expression or statement is incorrect--possibly unbalanced (, {, or [

I am writing cvx code for maximizing sum rate for NOMA. I am getting error as “Error: Expression or statement is incorrect–possibly unbalanced (, {, or [.” in this line x = evalin( ‘caller’, sprintf( '%s ', varargin{:} ) );.but this is a in built function…how to solve this error???

Please show us your code.