How to compare terms in column and set an if loop

I'm trying to do lexicographic rule on my matrix and I end up getting a column where two elements are the same. I need to set up an if loop for such an instance where two terms in the column are the same and I have to select one of them based on the index. What would be the code in this case

For example,

I got (5;3;3) as my column vector. If the terms are unique I could use the minimum function to capture the desired row. Otherwise I should choose the variable with the minimum value with another supporting condition. How do I formulate a loop in this case?

Answer 1

[KSSV]

You can find the difference and check when it is equal to zero and get its index.

X = [1 2 3 3 4 5 6] ; 
d = find(diff(X)==0) 

d = 3

X([d d+1])

ans = 1×2

3 3

Answer 2

[Voss]

Here is one way to pick the minimum value from each column, with space for you to write your own additional code in case of multiple elements in a column sharing the minimum value:

A = magic(6); % some matrix

A_min = min(A,[],1); % A_min is the minimum of each column of A

for i = 1:numel(A_min)
    
    idx = find(A(:,i) == A_min(i)); % find the rows of column i whose element is equal to the minimum element of column i
    
    if numel(idx) == 1
        % there is one and only one minimum in column i, located at row idx
        continue
    end
    
    % multiple elements of column i have the minimum value.
    % they are located at rows idx(1), idx(2), etc.
    
    % your code to pick among them goes here
    
end