MATLAB: Compare two tables and extract the columns similar to both

intersectMATLAB

Hi I have two data matrix, one is A and the other is B. I want to compare each column in A to B and if a match is found in B, then the whole column(s) in B should be extracted. In the attached file, under A, 11, 12, 13 and 14 can also be found in B. In this case all the values under 11, 12, 13 and 14 in B are extracted into C.

I tried using intersect but it doens't work.

Thanks!

Best Answer

If I understand correctly, then

C = B(:,ismember(B(1,:),A))

does what you want.

From your example, it looks like A is a row vector, and you want to compare it to the first row of B. That's what this code does.

Related Solutions

MATLAB: Finding similar rows in matrices

I think your best bet for something fast is the intersect() command.

doc intersect

for details. Be sure to use the "rows" argument.

Here is some code that I believe will do what you want, but I have to admit I did not test much:

a=[1,2,3;
1,3,5;
2,5,7];
b=[1,2,6;
1,4,8;
2,5,8];
c=[1,4,7;
1,5,3;
2,5,9];
[ab,ia,ib] = intersect(a(:,1:2),b(:,1:2),'rows')
[abc,iab,ic] = intersect(ab(:,1:2),c(:,1:2),'rows')
a_row_idx = ia(iab)
b_row_idx = ib(iab)
c_row_idx = ic

MATLAB: Intersect, Compare two columns or two matrix and extract common information

Here's a demo you can follow. It identifies rows of a matrix 'data' where the value in column 2 exactly matches the value in column 4.

% demo, random data
data = randi(3,12,4); 
% Find rows where value in col 2 exactly matches value in col 4

isMatch = data(:,2)==data(:,4);
% Put those rows into a new matrix

newMat = data(isMatch,:);

For floating decimals, 4.9999999 and 4.9999998 will not be an exact match. You can subtract the values from columns 2 and 4 and determine if the absolute value of their difference is less than some threshold you choose.

% Find rows where value in col 2 exactly matches value in col 4
isMatch = abs(data(:,2)-data(:,4)) < 0.0001; 
% Put those rows into a new matrix
newMat = data(isMatch,:);

Best Answer

Related Solutions

MATLAB: Finding similar rows in matrices

MATLAB: Intersect, Compare two columns or two matrix and extract common information

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