Subscripted assignment dimension mismatch.(matrices)

Question

cakey 2014-11-30

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/164782-subscripted-assignment-dimension-mismatch-matrices

评论： John D'Errico 2014-11-30

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
显示 6更早的评论隐藏 6更早的评论

cakey 2014-11-30

编辑：cakey 2014-11-30

在 MATLAB Online 中打开

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 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.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

the cyclist 2014-11-30

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/164782-subscripted-assignment-dimension-mismatch-matrices#answer_160670

在 MATLAB Online 中打开

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
显示 -1更早的评论隐藏 -1更早的评论

cakey 2014-11-30

在 MATLAB Online 中打开

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