MATLAB: How to select specific columns in a matrix and create a new one

create new matrixmatrixselect columnsselect rows

Hello, I am very new to Matlab, so my question could be too elementary… I have a huge matrix made of 7 rows. In the last row, there are only 1 or 0. I need to create a new matrix from the original one, taking only the columns which last row value is 1. Or, in other terms, I want to discard all those columns whose last value is 0. Is there a simple way to do it?

Thank you

Best Answer

Either

newmatrix = yourmatrix(:, yourmatrix(end, :) == 1)

newmatrix = yourmatrix(:, logical(yourmatrix(end, :)))

will do it.

This is very basic indexing so you should go through the Getting Started Tutorial. What the above does is:

get a logical row vector of which columns are 1 and which are 0, using either yourmatrix(end, :) == 1 or logical(yourmatrix(end, :)),
then use that logical vector of 0 and 1 to filter the column with yourmatrix(:, logicalvector)

Related Solutions

MATLAB: How to add a row and column to a matrix

One easy option is to do this for rows and columns separately

A = [1 2 3 ; 4 5 6 ; 7 8 9]
x = 3 ; % add a row/column of ones before this row/column
A(end+1, :) = 1 % add row add the end
A([x end], :) = A([end x], :) % swap the x-th and last row
% do the same for columns
A(:, end+1) = 1
A(:, [x end]) = A(:, [end x])

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eg:

Q = randi(456,10,15);
row=[1 2 5 4 3 6];
column=[5 7 3 4 8 14];
P = Q(sub2ind(size(Q),row,column));

EDIT

p = Q(row,column);
P = zeros(size(Q));
P(1:numel(row),1:numel(column)) = p;

Best Answer

Related Solutions

MATLAB: How to add a row and column to a matrix

MATLAB: Put smaller matrix in bigger matrix

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