MATLAB: Set specific values to NaN

nan

Hello everyone
My problem is as follows. I have a matrix like this for example:
A = [1 2 3 4 5 6 6 6 6; 
     2 4 3 5 4 6 7 7 7; 
     5 4 4 4 3 7 8 8 8; 
     2 1 3 3 3 3 3 3 5]'
Now i want to get a matrix which deletes the values which are similar (starting with the second) untill the end of the column. So columns 1, 2, 3 should delete some values while column 4 shouldn't delete any numbers.
At the end the matrix should look like this
A = [1 2 3 4 5 6 NaN NaN NaN; 
     2 4 3 5 4 6 7 NaN NaN; 
     5 4 4 4 3 7 8 NaN NaN; 
     2 1 3 3 3 3 3 3 5]'
I hope you get my problem. Thanks in Advance.

Best Answer

>> A = [1,2,5,2;2,4,4,1;3,3,4,3;4,5,4,3;5,4,3,3;6,6,7,3;6,7,8,3;6,7,8,3;6,7,8,5];
>> idx = cumprod(double(diff(flipud(A))==0),1);
>> idx(end+1,:) = false;
>> idx = logical(flipud(idx));
>> A(idx) = NaN
A =
     1     2     5     2
     2     4     4     1
     3     3     4     3
     4     5     4     3
     5     4     3     3
     6     6     7     3
   NaN     7     8     3
   NaN   NaN   NaN     3
   NaN   NaN   NaN     5
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