MATLAB: Remove the rows/columns with single values of a matrix

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Hello,
I have a matrix quite big (A < 23 x 250000 >). I want to evaluate the first row A(1,:) and eliminate the columns where there are values only repeated once. The number in this first row is an integer and always is increasing.
Lets say:
 B = [1    1    3    5    5    5    7    9    9
      0.1  0.5  0.2  0.4  0.3  0.9  0.1  0.6  0.5]
The result should be:
 B = [1    1    5    5    5    9    9
      0.1  0.5  0.4  0.3  0.9  0.6  0.5]
I know how to do it with for and if statements but I think it won't be efficient because the size of the matrix.
Many thanks!

Best Answer

This is the code I have and it works, but maybe it is not efficient:
 for i = 2:length(A) - 1;
    if A(1,i) ~= A(1,i-1) && A(1,i) ~= A(1,i+1)
        A = A(:,[1:i-1 i+1:end]);
        i = i - 1;
    end
 end
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