Subscripted assignment dimension mismatch.(matrices)

J = eye(4); % 4x4 identity matrix
u = sum(x);
N=[exp(cos(u))*sin(u),exp(cos(u))*sin(u),exp(cos(u))*sin(u),exp(cos(u))*sin(u);
    2*exp(cos(2*u))*sin(2*u),2*exp(cos(2*u))*sin(2*u),2*exp(cos(2*u))*sin(2*u),2*exp(cos(2*u))*sin(2*u);
    3*exp(cos(3*u))*sin(3*u),3*exp(cos(3*u))*sin(3*u),3*exp(cos(3*u))*sin(3*u),3*exp(cos(3*u))*sin(3*u);
    4*exp(cos(4*u))*sin(4*u), 4*exp(cos(4*u))*sin(4*u),4*exp(cos(4*u))*sin(4*u),4*exp(cos(4*u))*sin(4*u)];
for i=1:4
for j=1:4
J(i,j) = J(i,j) + N
end
end

But I get that error message, how can I make this work?

[the cyclist]

Can you put in a value of x (and any other values we need) that gives the error, so that we can run your code and see it for ourselves?

[cakey]

I use this: function p = newton(f,J,p0,tol) for i=1:50 p = p0 - J(p0)\f(p0); if norm(p-p0)<tol, break; end p0=p; end

then apply this : p1 = newton(f,@JJ,[2.5;2;1.4;.9],1.0e-12) f = @(x) x - exp(cos([1:4]*sum(x)));

[cakey]

And this code is for JJ

[cakey]

Am I missing something?

[cakey]

I think the dimension mismatch is with this: J(i,j) = J(i,j) + N

[cakey]

Okay, I looked and it says x is a 4 component column vector. So i am missing the definition for x?

[cakey]

Here it is. Now I keep getting an error for the matrix:

if true
  % code
end
function J = JJ(x)
J = eye(4); % 4x4 identity matrix
x=[exp(cos(u));
  exp(cos(2*u));
  exp(cos(3*u));
  exp(cos(4*u))]
u = sum(x);
N=[exp(cos(u))*sin(u),exp(cos(u))*sin(u),exp(cos(u))*sin(u),exp(cos(u))*sin(u);
  2*exp(cos(2*u))*sin(2*u),2*exp(cos(2*u))*sin(2*u),2*exp(cos(2*u))*sin(2*u),2*exp(cos(2*u))*sin(2*u);
  3*exp(cos(3*u))*sin(3*u),3*exp(cos(3*u))*sin(3*u),3*exp(cos(3*u))*sin(3*u),3*exp(cos(3*u))*sin(3*u);
  4*exp(cos(4*u))*sin(4*u), 4*exp(cos(4*u))*sin(4*u),4*exp(cos(4*u))*sin(4*u),4*exp(cos(4*u))*sin(4*u)];
for i=1:4
for j=1:4
J(i,j) = J(i,j) + N
end
end

if true
  % code
end

[John D'Errico]

Probably because in this latest code, you have written this as a function, where you pass in some variable x. But then you overwrite what you passed in as x, using a variable u, but you have not defined u until after x is created, as a function of u!

Perhaps you need to think about what you are trying to do.

Answer 1

[the cyclist]

It looks like N is a 4x4 matrix, and you are trying to assign it to just one position of J.

It is difficult to know what was intended here, instead of

for i=1:4
for j=1:4
J(i,j) = J(i,j) + N
end
end

maybe it should just be

J = J + N

That is just a pure guess, based on the size of the matrices.

[cakey]

I tried this, but still dimension mismatch. I'll try your way:

if true
  % code
end
function J = JJ(x)
x = [2.5; 2.0; 1.4; 0.9]
f = @(x) x - exp(cos([1:4]*sum(x)));
J = eye(4); % 4x4 identity matrix

if true
  % code
end
u = sum(x);
N=[exp(cos(u))*sin(u),exp(cos(u))*sin(u),exp(cos(u))*sin(u),exp(cos(u))*sin(u);
  2*exp(cos(2*u))*sin(2*u),2*exp(cos(2*u))*sin(2*u),2*exp(cos(2*u))*sin(2*u),2*exp(cos(2*u))*sin(2*u);
  3*exp(cos(3*u))*sin(3*u),3*exp(cos(3*u))*sin(3*u),3*exp(cos(3*u))*sin(3*u),3*exp(cos(3*u))*sin(3*u);
  4*exp(cos(4*u))*sin(4*u), 4*exp(cos(4*u))*sin(4*u),4*exp(cos(4*u))*sin(4*u),4*exp(cos(4*u))*sin(4*u)];
for i=1:4
for j=1:4
J(i,j) = J(i,j) + N
end
end

Answer 2

[John BG]

Have you tried 1. allocate initial J just after defining N to make sure J and N have same size with: J=zeros(size(N))

2. Instead of 2 for loops, would it be ok for you to use J=J'+N

John [e-mail]