Loop for creating Submatrix

Hey, I am still pretty new to MatLab and have Problems with creating a Loop that stores specific Data from one Matrix in a new one. To be precise, i need every fourth row of a Matrix ´forQ´ to create a ´nSim x 20´ Matrix where the first row refers to the fourth row of Matrix `forQ´, the second to the 9th of ´forQ´, the third to the 13th of `forQ´ and so on. However, when using the loop below, the rows of my resulting Matrix ´x´ consist only of the values in column 80 of Matrix ´forQ´.To be more precise, each value of e.g. row 1 in ´x´ is equal to the value of row 4, column 80 of ´forQ´. But this is not what i intended. Basically i want to copy ´forQ´s 1000 values in row 4 into row 1 of matrix x. I hope you understood the problem.

nSim=1000

x=zeros(nSim,20);

for c=1:20

for d=4:4:80

x(:,c)=forQ(:,d);

end

end

Thanks in andvance !!

Answer 1

[Asad (Mehrzad) Khoddam]

It should not be two nested loops. You can use one loop that increases a counter.

You can use this code that doesn't need a loop:

x = forQ(4;4:end, :);

[Claas-Christoph Seidel]

Thank you, you are absolutely right !