Why Matlab shows "Index exceeds matrix dimensions"?

%Linearized system
SIGMA = 10;
R = 28;
BETA = 8/3;

x=0;
y=1;
z=0;

   A=[-SIGMA, SIGMA,     0;
           R-z,    -1,    -x;
             y,     x, -BETA];

j=3;
dim=3;
N=3;
[Q,~] = qr(rand(dim,j),0);
c = [zeros(1,j-1) 1]; 
for i=1:N,
    QNew = A(: ,(i-1)*dim+1:i*dim)*Q; 
   [Q,~] = qr(QNew,0);
end
Q0=Q;
for i = (N+1):(2*N+1),
    QNew = A(: ,(i-1)*dim +1: i*dim)*Q; 
    [Q,R] = qr(QNew ,0);
    AllR = horzcat(R,AllR); 
end
numOfR = size(AllR,2)/j; 
for i = 1:numOfR
R = AllR(: ,(i-1)*j+1:i*j); 
cNew = R\c;
c = cNew/norm(cNew);
end
w=Q0*c;

I get the error "Index exceeds matrix dimensions.

Error in ginelli (line 21) QNew = A(: ,(i-1)dim+1:idim)*Q;"

Thanks in advance!

Answer 1

[Image Analyst]

A is 3-by-3. But i*dim can be 9 in the i=1:N loop or 21 in the i = (N+1):(2*N+1) loop. It doesn't have that many columns (9 or 21) - it has only 3.