Delete rows that have the first same value and keep one row in matrix with 2 colums?
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Hi everyone,
I have an array:
x=[0,0 ; 250,1050 ; 250,1051 ; 1173,3050 ; 1173 3150].
I don't know how to delete the rows that has the first value is 250 and just keep one.
The row may be (250,1050) or (250,1051), whatever but just one row.
Could someone please suggest me how to do it?
Many thanks.
2 Comments
Andrew Reibold
on 20 Nov 2014
Do you ONLY want the duplicated 250's removed, or ALL of the duplicated values removed (Like the duped 1173 as well)?
Accepted Answer
Matt
on 20 Nov 2014
Edited: Matt
on 20 Nov 2014
Khanh,
Try something like this. . .
ind250 = x(:,1) == 250;
if numel(ind250)>1
x(ind250(2:end),:) = [];
end
2 Comments
Andrew Reibold
on 20 Nov 2014
I think she needs it to work for all duplicates (like 1173 also), not just 250
More Answers (2)
C.J. Harris
on 20 Nov 2014
Do you mean something like this?
x = [0,0 ; 250,1050 ; 250,1051 ; 1173,3050 ; 1173 3150];
[~,idx] = unique(x(:,1));
out = x(idx,:)
out =
0 0
250 1051
1173 3150
2 Comments
Matt
on 20 Nov 2014
Note that the unique will remove all non-unique values, not just the ones with 250 in the first column. Still, if this is the goal, than this is a much better solution than removing elements one by one
Andrew Reibold
on 20 Nov 2014
Edited: Andrew Reibold
on 20 Nov 2014
This removes any rows where the value in the first column has already been used.
[~,idx] = unique(x(:,1)); %which rows have a unique first value?
x = x(idx,:) %only use those
Output:
x =
0 0
250 1050
1173 3050
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