How to make array with first values of matrix

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

[Jan]

Do not post multiple threads for one problem. See https://www.mathworks.com/matlabcentral/answers/384217-how-to-make-an-array-with-specific-matrix-values

Answer 1

[C.J. Harris]

% 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);

[Jan]

Use true instead of boolean(1).