remove rows by pick the min value in another column

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booterr
booterr 2016-4-14
评论： booterr 2016-4-15
Can you help?
On below matrix, for same X and Y, pick smallest Z, then put into a new matrix by removing the rows? and also give the row number for which row is kept.
X Y Z
60,-40,1.1
55,-40,3.1
55,-45,4.5
60,-45,5.3
60,-40,7
55,-40,8.4
55,-45,9.8
60,-40,11.2
60,-45,12.6
55,-40,14
55,-45,15.4
60,-45,16.8
60,-40,18.2
60,-45,19.6
55,-40,21
60,-40,22.4
55,-45,23.8
60,-45,25.2
55,-40,26.6
55,-45,28
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booterr
booterr 2016-4-15
not a duplicate questions. For the first thread, the answer did not give which row number the Z is located in the initial matrix.
I am not only needing the value of Z, but also need the row number of which Z is outputted.
thanks

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Andrei Bobrov
Andrei Bobrov 2016-4-15
编辑：Andrei Bobrov 2016-4-15
x=[55,-45,9.8
60,-40,11.2
60,-45,12.6
55,-40,14
55,-45,15.4
60,-45,16.8
60,-40,18.2
60,-45,19.6
55,-40,21
60,-40,22.4
55,-45,23.8
60,-45,25.2
55,-40,26.6
55,-45,28]
[a,~,c] = unique(x(:,1:2),'rows');
n = size(a,1);
valuemin = zeros(n,4);
for ii = 1:n
i0 = find(c == ii);
[valuemin(ii,3),i1] = min(x(i0,end));
valuemin(ii,[1:2,4]) = [a(ii,:),i0(i1)];
end
or
[a,~,c] = unique(x(:,1:2),'rows');
idx = accumarray(c,(1:size(x,1))',[],@(y)y(min(x(y,3))==x(y,3)));
valuemin = [a,x(idx,3),idx];

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