storing a matrix using new variables established by 'eval'

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?

Answer 1

[the cyclist]

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

[Franco]

That really is much better...thanks a bunch!

Answer 2

[Jiro Doke]

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.

[Franco]

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]

@Franco: A CELL vector seems to be the best soltution for your problem.