Undefined function 'symsum' for input arguments of type 'double'

Can someone please explain me why I have this error? I was trying to do a sum of observations yij (observation i, replica j).

function [ yij ] = SPCmethod(yij,w)
          sym n;
          rep = 100;
          for i = 1:w
              yij(i) = mean (symsum(yij,i,1,rep))/rep
          end

Answer 1

[Veera Kanmani]

First you need to

syms n

not sym n

[Walter Roberson]

That is not the problem, because they do not use n, so having an extra command equivalent to

sym('n');

will not cause any problems.