Error in sum statement

I have Matrix,

I =[5 6 7 8;2 8 6 3;4 0 4 2;5 0 1 0];
r = size(I,1);
c= size(I,2);
N = r*c;
Ik = I(r,c);
A = unique(I);
Nk= [A,histc(I(:),A)];
for s=0:r
 for d= 0:c
Xt= symsum((Ik*Nk)/N,s,d);
end
end

My Question >> error in symsum statement is "undefind function 'symsum' for input arguments of type 'double' please, help me

[Torsten]

I don't see any symbolic variables used in your code (which were necessary for symbolic summation).

Best wishes

Torsten.