MATLAB: How to create a vector of ratios from columns in a matrix

arrayfor loopif statementMATLABmatrixmatrix manipulation

I need to determine the ratio of elements above 30 in each column of a matrix and save in a vector. My current code looks like this:
function output = ratiomatrix(a)
%address all rows, by each column do previous ratio
%but divide by number of elements in column
%probably do it inside for loop and put in vector
[rows,columns] = size(a); %gets number of rows and columns (divide by rows for ratios)
greater = 0; %initialise variable for loop
output = zeros(1,columns); %preallocate variable for greater speeeeeed
for i = 1:columns 
    for j = 1:rows
        if a(j) > 30
            greater = greater + 1;
            output(i) = greater/rows;
        end
    end
    %output(i) = greater/rows;
    %greater = 0;
end
end
The problem i am currently having is that with each iteration, the value of greater includes the previous column and so gives my the wrong ratio. I have tried setting greater back to zero in a number of different places but this does not help. I would appreciate some hints as to how I might fix this, maybe without a complete answer if that's possible?

Best Answer

Since ‘a’ is a matrix, you likely have to use two subscripts to it in your if statement, not one.
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