What should I do to fix "warning: implicit conversion from real matrix to real scalar"?

[John B. Thoo]

Hi, everyone.

I have a 512 x 161 matrix of values  u(x,t)  saved in a file  
"ht_tf8M160ord9visc01.mat".

I write a function and invoke quad in a file "energy.m" thus:

%%--------begin energy.m---------
1;

function y = h (x)

load ht_tf8M160ord9visc01.mat u;
x = u(:,5);

  y = x.^2;

endfunction

quad ("h", 0, 1)
%%---------end energy.m----------

then I get this:

octave-3.0.5:31> energy
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
warning: implicit conversion from real matrix to real scalar
ans =  0.16711
octave-3.0.5:32>

What should I do to fix the warning "implicit conversion from real  
matrix to real scalar"?

Btw, my eventual goal is to define a function  P(t) = \int H(u(:,t))  
dx  for some function H(x).  Does it look like my M-file is on the  
right track?

Thanks for your help.

---John.