MATLAB: Quickly access a group of arrays using a loop

arrayevalloop

Hi,

I have a set of arrays labeled as "A1", "A2", "A3"…"An" What I would like to do is write a loop that allows me to access each without having to type the array names out individually. For instance if I wanted to access the first entry of each array:

for i=1:n A "i" (1) end

I've been messing with num2str and eval but I can't seem to get something that works. Any pointers would be appreciated.

Cheers, David

Best Answer

Using num2str() and eval() should be able to do it. See this post for details. But it is highly recommended not to name variable as A1, A2, A3,... as you now see the problem.

http://www.mathworks.com/matlabcentral/answers/143-how-do-i-make-a-series-of-variables-a1-a2-a3-a10

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The best thing to do would be to move the plotting outside the loop:

...
end
figure(1);
plot(xra,yra,'k.');

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Avoid the usage of eval when you need a fast program, and in all other cases also.

Instead of creating the strings 'theta(1).*theta(1)' it would be smarter to store the indices only:

A = {[1,1], [1,2], [1,3]; ...
     [2,1], [2,2], [2,3]; ...
     [3,1], [3,2], 3,3]};
for i = 1:n
  for j = 1:n
    index = A{i, j};
    a(i,j) = theta(index(1)) * theta(index(2));
  end
end

Using a numerical 3D array might be even faster.

Creating files dynamically has the big disadvantage, that reading and parsing the M-files is very time-consuming. Matlab is much more efficient, if you use static M-files and vary the parameters only.

Best Answer

Related Solutions

MATLAB: Quick itteration

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