Why wont the divide operator work?

A = [1 2 1; 2 1 2; 1 2 1];
b = [1; 1; 1];
x = [6; 6; 6];
r = b-a*x;
p = r;
w = zeros(3);
tolerance = 10^(-6);
k = 0;
while norm(r) > tolerance
    plot(k,log(norm(r))^2)/(dot(p,A*p));
    x = x*p;
    r1 = r - a*A*p;
    b = (norm(r))^2/((norm(r))^2);
    r=r1;
    p=r1+b*p;
end

The script is returning an error on the divide operator in the code "plot(k,log(norm(r))^2)/(dot(p,A*p))..." why?

Answer 1

[Mischa Kim]

Julia, are you showing all the code? Looks like the variable a is not defined.

As for the plot command: one of the round brackets is misplaced. The way it is typed right now, MATLAB thinks that the command ends after the 2.

 plot(k,log(norm(r))^2)  /(dot(p,A*p));