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matlabvariablesfor-loopmatrix
cacá
cacá

Reputation: 85

matlab: creating additional variables in a for loop

I got the following problem: In my code I want a matrix-...-matrix-vector in a for loop. In every loop I want to get an additional matrix to multiply with, e.g. i=1: P1*z and i=2: P1*P2*z etc. This is my code so far. Obviously it is just computing: i=1: P1*z, i=2: P2*z etc...

for ii = 1:10
    % Projection on last_z
    projected_last_z = projection(:,:,ii) * last_z;
end

Upvotes: 0

Views: 56

Answers (2)

Ikaros
Ikaros

Reputation: 1048

You must do compute the value always in the same variable if you want to keep the results

n = 10;
projected_last_z = 1;
for ii = 1:n
    projected_last_z = projected_last_z * projection(:,:,ii);
end
projected_last_z = projected_last_z * last_z;

The loop is

loop 1 : projected_last_z = P1

loop 2 : projected_last_z = P1 * P2

...

loop 10 : projected_last_z = P1 * P2 * ... * P10

Then you multiply the final result by last_z

Upvotes: 1

Bas Swinckels
Bas Swinckels

Reputation: 18488

It is usually considered bad practice to create new variables in a loop as you want. Better to collect all the results in a cell array or so: 

n = 10;
results = cell(1, n);  % preallocate some space
for i = 1:n
    results{i} = some_calculation(i);
end;

You can then retrieve the result of the k-th iteration using results{k}.

Upvotes: 1

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