# How can I put the outputs of for loop into a matrix?

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Eray Bozoglu on 30 Nov 2020
Commented: Eray Bozoglu on 1 Dec 2020
Hey i am new to matlab and need help with storing answer of my for loop into a matrix can anyone help ?
my aim is having (n x n) matrix. thanks a lot
for j=1:n
for i=1:n
a=(5*(i/n))+(8*(j/n));
end
end

Rik on 30 Nov 2020
You are overwriting a. What is your goal?
Eray Bozoglu on 30 Nov 2020
edited the post im trying to have (n x n) matrix. with the current code if i plug 2 i can have 4 out put. such as
a b c d
i want to have them stored as [a b ; c d]
so for bigger n i can have better overview and use it in another script with defining it as a matrix.
Rik on 30 Nov 2020
You are still overwriting a in every iteration.
Did you do a basic Matlab tutorial?

John D'Errico on 30 Nov 2020
Edited: John D'Errico on 30 Nov 2020
First, don't use loops at all. For example, with n==3...
n = 3;
ind = 1:n;
a = ind.'*5/n + ind*8/n
a = 3×3
4.3333 7.0000 9.6667 6.0000 8.6667 11.3333 7.6667 10.3333 13.0000
Since this is probably homework, and a loop is required, while I tend not to do homework assignments, you came pretty close. You made only two mistakes. First, you did not preallocate a, which is important for speed, but not crucial. It would still run without that line. Second, you are stuffing the elements as created into a(i,j). So you need to write it that way.
n = 3;
a = zeros(n); % preallocate arrays
for i = 1:n
for j = 1:n
a(i,j) = (5*(i/n))+(8*(j/n));
end
end
a
a = 3×3
4.3333 7.0000 9.6667 6.0000 8.6667 11.3333 7.6667 10.3333 13.0000

#### 1 Comment

Eray Bozoglu on 1 Dec 2020
thanks a lot