Delete row and column from matrix

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Rachel Ramirez
Rachel Ramirez 2020-12-9
回答： Kedar Ingle 2020-12-9
I have matrix A that is 100x5 and a matrix B that is 10x2. I want to go through matrix A and delete all rows that have matrix B first column values in matrix A but only from it's first and/or second column (not the other 3). I'm thinking of a foor loop and and if statement inside but not sure how to. Could you someone elaborate how to approach the problem?
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KSSV
KSSV 2020-12-9
Read about ismember. This will give you indices which are common in both the matrices.

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回答（1 个）

Kedar Ingle
Kedar Ingle 2020-12-9
It is my understanding that you want to remove rows from matrix A whose elements in column 1 or 2 come from column 1 of matrix B?
The checking of whether matrix A elements (from columns 1 and 2) are present in matrix B (column 1) could be done with the function ismember. The solution could look something like this:
function [output] = reduceA(A,B)
i=1;
while i <= size(A, 1) % while not for, as the loop size keeps on reducing
if(ismember(A(i,1), B(:, 1)) || ismember(A(i,2), B(:, 1)))
A(i, :) = [];
else % only increment the counter if we haven't deleted a row...
i = i + 1;
end
end
output = A;
end

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