MATLAB: Selecting the highest value

datamining

I have dataset of 5 columns
    1  3   .5      .6    89
    1  2    03     .6    98
    1  8   .3      .3    90
    2  3   .2      .5    87
    2  87   02      1    89
    ;
    ;
    ;
    ;
    10  12  01      .3    87
    10  12  03       07   99
    10  0.3 0.5      10    78
i want to select highest values in column 5 for erach unique value,i nees as
1  8   .3      .3    90
2  87   02      1    89
10  12  03       07   99
please help

Best Answer

I don't understand why the first row of your result is not
1  2    03     .6    98
as 98 is bigger than 90. Assuming you've made a mistake, the following code works, though there may, as ever, be neater methods:
data = [1  3   .5      .6    89
    1  2    03     .6    98
    1  8   .3      .3    90
    2  3   .2      .5    87
    2  87   02      1    89
    10  12  01      .3    87
    10  12  03       07   99
    10  0.3 0.5      10    78];
indexcol = 1;
valuecol = 5;
indexlist = data(:,indexcol);
indexes = unique(indexlist);
results = zeros(length(indexes), size(data,2));
for k = 1:length(indexes)
    rows = find(indexlist == indexes(k));
    [unused, maxsubsetrow] = max(data(rows, valuecol));
    maxrow = rows(maxsubsetrow);
    results(k, :) = data(maxrow, :);
end
disp(results);
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