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Obtain lines of a matrix according to its position.

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Hi. Good day.
I hope you help me solve this problem.
I have a matrix A of size 4 X 18.
I have the positions of the lines(row) that interest me to know.
For example I have the positions of lines(row) 2 and 4 and now I am interested in "" taking out "" of the matrix A the values ​​of lines(row) 2 and 4 and with these values ​​forming a matrix B
A=[ 10 87 11 10 10 10 13 10 76 82 87 89 86 10 13 88 12 90
. 84 70 76 86 90 10 10 80 69 71 72 83 68 84 11 76 10 83
. 91 99 94 10 85 80 10 88 84 88 11 10 78 81 82 86 11 86
. 71 73 74 76 73 67 86 77 76 78 86 89 78 73 79 73 91 79 ];
This would be the matrix B
B=[84 70 76 86 90 10 10 80 69 71 72 83 68 84 11 76 10 83
. 71 73 74 76 73 67 86 77 76 78 86 89 78 73 79 73 91 79]
The actual matrix A I have is 720 X 18
Thank you.
Regards.

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Diana Mae Calde
Diana Mae Calde on 3 Oct 2019
Matrix is equal m x n where m is number of rows and n is number of columns
A = 720 x18 and you want a specific row to be in B
B = A(2,:); for row 2
but if you need multiple of 2
size = size(A)
for n = 1:size(1)
B = A(n,:);
n = n + 2
end

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Accepted Answer

Stephen Cobeldick
Stephen Cobeldick on 3 Oct 2019
Edited: Stephen Cobeldick on 3 Oct 2019
All you need is some very basic indexing:
B = A([2,4],:)
Very basic MATLAB concepts, like how to use indexing, are explained in the introdutory tutorials:

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