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# How to make array with first values of matrix

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Filip Konecny on 22 Feb 2018
Commented: Jan on 22 Feb 2018
Hello to all,
I have a matrix for example like this: [1 2 3 4 5 6 7 8 9 10;2 2 3 3 4 5 5 2 3 3]' the first column represents time, the second ID of time. I need to make a cycle which goes through the matrix and takes the first time value from the group of ID of time.
So in this case the result will be: [1 3 5 6 8 9].
unique function is unfortunately not helpful in this case because the groups of ID of time might repeat.
Thank you very much
Filip

#### 1 Comment

Jan on 22 Feb 2018

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### Answers (1)

C.J. Harris on 22 Feb 2018
% Input
A = [1 2 3 4 5 6 7 8 9 10;2 2 3 3 4 5 5 2 3 3]';
% Result
B = A([boolean(1); diff(A(:,2))~=0],1);

#### 1 Comment

Jan on 22 Feb 2018
Use true instead of boolean(1).

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