MATLAB: Delete columns of a matrix based on values in other matrix

deleteindexingmatrix

I have 3 matrices. The 2nd column of Matrix #1 counts up from 1 to 200. I want to check the 4th column of matrix #2 and the 10th column of matrix #3. If Matrix #1 contains a value in col2 that matrix 2 col4 or matrix 3 col10 does not have, i want to delete or turn the whole row containing that uncommon values to zeros.
Ex.
Matrix 1 (col2) Matrix 2 (col4) Matrix 3 (col10)
1 2 1
2 3 2
3 4 3
4 5 4
5 7 5
6 8 7
7 9 9
8 10 10
9 11 11
10 12 12
…
In this case, i am looking for rows 1, 6 and 8 to be deleted(or turned to zeros) from Matrix 1. Row 6 of Matrix 2 and row 1 of matrix 3.
Thanks

Best Answer

Replaces identified rows with zeros.
% Example data that match the indices in your question
M1 = rand(10,10);  M1(:,2) = 1:10; 
M2 = rand(10,10);  M2(:,4) = [2:5,7:12];
M3 = rand(10,10);  M3(:,10) = [1:5,7,9:12]; 
% Identify rows that should be eliminated; replace data with zeros.
idx = ~ismember(M1(:,2),M2(:,4)) | ~ismember(M1(:,2),M3(:,10)); 
M1(idx,:) = 0;
Note that row 6 should also be altered in addition to row 1 and 8.
If you'd rather delete those rows in M1 rather than replace the values with 0s,
M1(idx,:) = [];
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