Computing the median of a group except one member
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I have a dataset of a variable x for S seasons of the same J firms (not ordered). I'd like to compute for each firm in each season, the median of all other firms in that season. e.g. S=2, J=6, my dataset is
M=[1 2 3 6 5 4 2 3 4 1 5 6; 1 1 1 1 1 1 2 2 2 2 2 2; 2 4 6 5 7 8 3 7 5 7 5 3]'
First column is the firm index, second column the season, third column the x values for each firm in each season.
I am thinking something like
for i=1:size(M,1)/6
for j=6*i-5:6*i
M(j,4)=median(M(6*i-5:6*i,3));
end
end
but with the index of M(:,3) inside median() somehow telling MATLAB to exclude the jth entry of M(:,3)?
Thank you!
8 Comments
madhan ravi
on 14 Feb 2019
ok did you get the answer to your question since you accepted the answer ?
Accepted Answer
Kevin Phung
on 14 Feb 2019
Hello!
Is this sort of what you're looking for?
M=[1 2 3 6 5 4 2 3 4 1 5 6; 1 1 1 1 1 1 2 2 2 2 2 2; 2 4 6 5 7 8 3 7 5 7 5 3]';
num_seasons = unique(M(:,2)); %num of seasons
num_f = unique(M(:,1)); %num of firms
for i = 1:numel(num_seasons) % for each season...
season = M(M(:,2) == num_seasons(i),:); %matrix of season being iterated
for j = 1:numel(num_f) % for each firm...
med = median(season(not(season(:,1)==num_f(j)),3)); %median of OTHER firms for the season
disp(['Firm: ' num2str(num_f(j)) ' Season:' num2str(num_seasons(i)),...
' Median: ' num2str(med)]);
end
end
6 Comments
Kevin Phung
on 14 Feb 2019
Just for the sake of following up with my mistake:
I made the mistake of converting the values into strings. row should have been:
row = all(M(:,[1 2])==[num_f(j) num_seasons(i)],2); %locate row where firm and season matches
so this should have worked:
M=[1 2 3 6 5 4 2 3 4 1 5 6; 1 1 1 1 1 1 2 2 2 2 2 2; 2 4 6 5 7 8 3 7 5 7 5 3]';
M(:,4)=0; %create column of zeros
num_seasons = unique(M(:,2)); %num of seasons
num_f = unique(M(:,1)); %num of firms
for i = 1:numel(num_seasons) % for each season...
season = M(M(:,2) == num_seasons(i),:); %matrix of season being iterated
for j = 1:numel(num_f) % for each firm...
med = median(season(not(season(:,1)==num_f(j)),3)); %median of OTHER firms for the season
row = all(M(:,[1 2])==[num_f(j) num_seasons(i)],2); %locate row where firm and season matches
M(row,4) = med; %append the median to the corresponding row, 4th col
end
end
use whichever method works best for you
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