Finding differences between two vectors in an explicit way.

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!

[Ajay Kumar]

Are there only single digit values in vec1 and vec2?

If not how are double and tripe digits are differed from vec1 and vec 2?

for example: how is 111 referred as? 555?

[Jenna Wong]

Yes, only single digit values. In this case, where vec1 is a list of true class labels, and vec2 is a list of predicted class labels, I would expect 111 and 555 to be distinct separate classes, so they would just be the actual numbers:

vec1 = [5 4 2 1 3 1 1 1 4 111]

Answer 1

[the cyclist]

% 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'];

[Jenna Wong]

Thank you, that works perfectly! I need to learn how to use the function "unique" more often.