# Indexing with conditions for certain columns

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Yaser Khojah on 22 Mar 2019
Commented: Walter Roberson on 25 Mar 2019
I have a huge matrix where I want to find the indexes that meet each column median only and the rest of the column median should not be included. A manual way to do it is written as below but I need an easier way since my matrix is huge. Thank you so much in advanced.
Matrix_All = rand(1000,3) * 100;
Median_All = median(Matrix_All);
idx_1 = find( Matrix_All(:,1) == Median_All(1) & Matrix_All(:,2) ~= Median_All(2) & Matrix_All(:,3) ~= Median_All(3));
idx_2 = find( Matrix_All(:,1) ~= Median_All(1) & Matrix_All(:,2) == Median_All(2) & Matrix_All(:,3) ~= Median_All(3));
idx_3 = find( Matrix_All(:,1) ~= Median_All(1) & Matrix_All(:,2) ~= Median_All(2) & Matrix_All(:,3) == Median_All(3));
Mat_1 = Matrix_All(idx_1,:);
Mat_2 = Matrix_All(idx_2,:);
Mat_3 = Matrix_All(idx_3,:);
Yaser Khojah on 25 Mar 2019
Dear Guiliaume, Sorry I could not get back to you since I did not have access to my MATLAB. Below is what i want to do but not manually since I have to find do that for different criteria.
idx_1 = MaT_All(:,1) == Median_All(1) & MaT_All(:,2) ~= Median_All(2)...
& MaT_All(:,3) ~= Median_All(3) & MaT_All(:,4) ~= Median_All(4)...
& MaT_All(:,5) ~= Median_All(5) & MaT_All(:,6) ~= Median_All(6)...
& MaT_All(:,7) ~= Median_All(7) & MaT_All(:,8) ~= Median_All(8);
Mat_1 = MaT_All(idx_1,:);
scatter(MaT_All(idx_1,18),MaT_All(idx_1,17)); hold on;
idx_2 = MaT_All(:,1) ~= Median_All(1) & MaT_All(:,2) == Median_All(2)...
& MaT_All(:,3) ~= Median_All(3) & MaT_All(:,4) ~= Median_All(4)...
& MaT_All(:,5) ~= Median_All(5) & MaT_All(:,6) ~= Median_All(6)...
& MaT_All(:,7) ~= Median_All(7) & MaT_All(:,8) ~= Median_All(8);
Mat_1 = MaT_All(idx_2,:);
scatter(MaT_All(idx_2,18),MaT_All(idx_2,17)); hold on;
Is it because if the median is found multiple time you only pick one answer where in my case I select all of them?

Walter Roberson on 22 Mar 2019
matches_median = bsxfun(@eq, MaT_All, Median_All);
matches_one = find(sum(matches_median,2) == 1);
matches_which = 1 + sum( cumprod(~matches_median(matches_one,:), 2), 2 );
Mat = cell(8,1);
for G = 1 : 8
Mat{G} = MaT_All(matches_one(matches_which==G),:);
end
##### 2 CommentsShowHide 1 older comment
Walter Roberson on 25 Mar 2019
The data you have provided us only has 10 columns, so looking at column 18 vs column 17 does not make any sense to us.