How to obtain ORIGINAL columnar indexes of top 3% values.

I need to obtain the top 3% of values from each column of an array, along with their respective indexes. I've sorted and selected the top 3% of values, and this portion of the code works, but I'm unsure of how to obtain the index of these values BEFORE they are sorted.

x = [1 3 5; 1 23 9; 123 34 75]; % Create Data

[rows,columns] = size(x); %Define rows, columns

for q = 1:columns

xSort = sort(x(:,q),'descend'); % Sort Descending

top3percentx = xSort(1:ceil(length(xSort)*0.03)); % Desired Output (top 3%)

end

Answer 1

[madhan ravi]

https://www.mathworks.com/help/matlab/ref/sort.html#bt8nojg-1-I - see the second output of sort()

Answer 2

[Stephen23]

mat = [1,3,5;1,23,9;123,34,75];
idy = 1:ceil(size(mat,1)*0.03);
for k = 1:size(mat,2)
    [vec,idx] = sort(mat(:,k),'descend');
    vec(idy) % top 3% values
    idx(idy) % and their indices
end

Answer 3

[Star Strider]

Another option, using the maxk function (introduced in R2017b):

x = rand(100, 3);                                   % Create Data
[Top3pct,RowIdx] = maxk(x,ceil(size(x,1)*0.03))

This eliminates the (explicit) sort call, and appears to do what you want.