Extracting rows form a matrix with indices.
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Paola on 21 Feb 2023
Commented: Paola on 23 Feb 2023
i have a Matrix a=(24X30) and a vector b=(1,4,7,8,10,12) that represents the rows index. I would like to create a new Matrix C=(6X30). This matrix is composed of the 6 rows with indeces (1,4,7,8,10,12), the vector b.
How can I do that?
dpb on 21 Feb 2023
Edited: dpb on 21 Feb 2023
M=[[1:24].' randi(100,24,5)]; % a sample array
b=[1,4,7,8,10,12]; % the indexing vector
N=M(b,:) % the new array
illustrates vector indirect addressing does work.
NOTA BENE: the array M was created such that the first element is the row index value so can see which was selected by inspection to prove got what wanted...
More Answers (1)
Adam Drake on 21 Feb 2023
% Create Matrix A: 24 x 30
A = randi(100,[24 30]);
% Create Vector B: desired row indices
B = [1,4,7,8,10,12];
% Create Matrix C: desired rows from Matrix A, specified by B
C = A(B,:);
The desired rows are specified by B, all columns are specified by ':'.
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