function index_dups = find_repeats (output)
%
% Function finds the same station and niskin bottle number in output and
% calls these "duplicate" samples.
%
% want to find duplicates of 
% station number and niskin number
%
% II should be (number_duplicate, 2) array of the indeces of all duplicates
%
% Version 1:  written for Clivar output files that had station, cast, niskin, etc.
% Version 2: written for AOML files that have station, niskin, etc.
%   Output = 
%       column 1 = output_sta  
%       column 2 = output_niskin
%       column 3 = output_bottle (sample bottle number or run order number)
%       column 4 = output_twiceratio 
%       column 5 = output_salinity 
%       column 6 = output_quality
%       column 7 = output_cast 
%
I_column_station = 1;
I_column_niskin = 2;

num_duplicates = 0;
index_dups = [];
for II = 1:length(output)
    i_check_sta = output(II,I_column_station);
    i_check_niskin = output(II,I_column_niskin);
    JJ = find(output(:,I_column_station) == i_check_sta & output(:,I_column_niskin) == i_check_niskin);
    if length(JJ) > 1
        % found a duplicate       
        num_duplicates = num_duplicates + 1;
        index_dups(:,num_duplicates) = JJ;
    end
end
if isempty(index_dups)
    fprintf(1,'\nNo Duplicates Found\n\n')
else
    index_dups=unique(index_dups','rows');
end
return;