How to find first two maximum number in the matrix

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Hello everyone,
I have the following matrix A (right table):
A = [1248,30,12;1248,20,13;1248,5,14;177,5,12;177,25,13;230,10,14;230,40,15;274,60,12;274,5,14];
I want to find the matrix B (left table) in the way that first, check the column "ID" to find the similar ID, then find the first two max number and finally find the "PE" related to the found first two max number. For example, first it will find that ID = 1248 has three repetitions. Then, from TE, it will find that 30 and 20 are the first two max numbers. And finally, it will find 12 (for max 30) and 13 (for max 20). Can anyone help how to search for that unique id

Accepted Answer

Andrei Bobrov
Andrei Bobrov on 23 Oct 2015
Edited: Andrei Bobrov on 23 Oct 2015
[a,~,c] = unique(A(:,1),'stable');
a0 = sortrows([c,A(:,2:end)],[1,-(2:3)]);
i1 = bsxfun(@plus,find([1;diff(A(:,1))~=0]),0:1)';
out = [a,reshape(permute(reshape(a0(i1,2:end),2,[],2),[1,3,2]),4,[])'];
a = unique(A(:,1),'stable');
n = numel(a);
out = zeros(n,5);
for ii = 1:n
l0 = a(ii) == A(:,1);
b = sortrows(A(l0,2:end),-(1:2));
out(ii,:) = [a(ii),reshape(b(1:2,:),1,[])];

More Answers (1)

TastyPastry on 19 Oct 2015
Assuming there are at least 2 values for TE/PE for each ID:
uniqueVals = unique(A(:,1),'stable');
output = zeros(numel(uniqueVals),5);
for i = 1:numel(uniqueVals)
mask = A(:,1) == uniqueVals(i);
[sorted,ind] = sort(A(mask,2),'descend');
PE = A(mask,3);
newRow = [uniqueVals(i) sorted(1:2) PE(ind)];
output(i,:) = newRow;
TastyPastry on 23 Oct 2015
newRow = [uniqueVals(i) sorted(1:2)' PE(ind(1:2))'];
This code still only works if each ID has two values of TE and PE associated with it. It will error on the last line ID = 811 as shown above.

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