storing a matrix using new variables established by 'eval'

2011 2 3
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I am trying to get a for loop introduce a new variable for every loop using the 'eval' function and store a matrix in the new variable.
elements = 3;
nodes = 2;
phi = [pi / 3,pi-pi/3,0];
for i = 1:elements
eval(['stiffness_' num2str(i) '=zeros(2)'])
eval(['stiffness_' num2str(i) '=[(cos(phi(i)))^2,sin(phi(i)) * cos(phi);sin(phi(i)) * cos(phi(i)),(sin(phi(i)))^2]'])
end
but it's not working. Anyone out there know how to do this?

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the cyclist
the cyclist 2011-2-3

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There were two syntax errors:
  • Extra bracket at the end of the last line.
  • In one of the terms, you forgot to index into phi(i), using instead just "phi".
More importantly, there is a much better way to code this, using cell arrays. (Notice, in my code below, the curly brackets indexing into the variable "stiffness".) Search the documentation for "cell array" for details. You'll be glad you did.
elements = 3;
nodes = 2;
phi = [pi / 3,pi-pi/3,0];
for i = 1:elements
stiffness{i}=zeros(2)
stiffness{i}=[cos(phi(i))^2,sin(phi(i)) * cos(phi(i));sin(phi(i)) * cos(phi(i)),sin(phi(i))^2]'
end
There is also a good explanation here:
http://www.mathworks.com/matlabcentral/answers/143-how-do-i-make-a-series-of-variables-a1-a2-a3-a10

更多回答（1 个）

Jiro Doke
Jiro Doke 2011-2-3

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I think you asked a similar question here.
There are better ways to do this. Take a look at the answers presented in your other post.

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Franco
Franco 2011-2-3
I know I can store the variables in a vector, but I really need them as serate variables. Eventually they turn into matrices and things get complicated if they aren't kept separate.
Jan
Jan 2011-5-20
@Franco: A CELL vector seems to be the best soltution for your problem.

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