MATLAB: Finding differences between two vectors in an explicit way.

classificationcomparedifferencesMATLAB

I am trying to compare two vectors, let's say
vec1 = [5 4 2 1 3 1 1 1 4];
vec2 = [5 4 2 5 3 2 1 2 2];
As you can see, they differ in indices 4, 6, 8, 9. I would like to determine how they differ, so that I get the following information:
The number 1 from vec1 is classified as a 5 in vec2 one time.
The number 1 from vec1 is classified as a 2 in vec2 two times.
The number 4 from vec1 is classified as a 2 in vec2 one time.
I would like to get it as a numerical result so that it is easier to work with, e.g.:
[1 5 1
1 2 2
4 2 1];
These vectors will be very long. Is there a fast way to go about this? Thank you all!

Best Answer

% Input vectors
vec1 = [5 4 2 1 3 1 1 1 4];
vec2 = [5 4 2 5 3 2 1 2 2];
% Identify the mismatched rows, and create a matrix of them
idx = vec1~=vec2;
mismatchedRows = [vec1(idx); vec2(idx)]';
% Find the *unique* mismatched rows, and the indices from the unique ones
% back to the original ones
[uniqueMismatchedRows,~,indexBacktoOriginal] = unique(mismatchedRows,'row','stable');
% Count the number of occurrences of each mismatch row
count = histcounts(indexBacktoOriginal,[unique(indexBacktoOriginal); Inf]);
% Put it all together for the output
output = [uniqueMismatchedRows count'];
Related Question