Subscripted assignment dimension mismatch.(matrices)

2014 11 30
2 个回答
回答已采纳
更新时间：2014 11 30
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0 个投票

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?

8 个评论
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the cyclist
the cyclist 2014-11-30
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
cakey 2014-11-30
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
cakey 2014-11-30
And this code is for JJ
cakey
cakey 2014-11-30
Am I missing something?
cakey
cakey 2014-11-30
I think the dimension mismatch is with this: J(i,j) = J(i,j) + N
cakey
cakey 2014-11-30
Okay, I looked and it says x is a 4 component column vector. So i am missing the definition for x?
cakey
cakey 2014-11-30
编辑：cakey 2014-11-30
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
John D'Errico 2014-11-30
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.

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 采纳的回答

the cyclist
the cyclist 2014-11-30

0 个投票

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.

1 个评论
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cakey
cakey 2014-11-30
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

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更多回答（1 个）

John BG
John BG 2014-11-30

0 个投票

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 jgb2012@sky.com

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