# How to merge adjacent NaN values into single NaN value in a vector?

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Mr M. on 1 Jul 2018
Edited: Stephen23 on 3 Jul 2018
I have [1 2 3 NaN NaN 0 1 2 NaN 9 8 7 6 NaN NaN NaN 1 1] anf I want [1 2 3 NaN 0 1 2 NaN 9 8 7 6 NaN 1 1] without a for cycle. Are there any trick to do this?
Stephen23 on 1 Jul 2018

Stephen23 on 1 Jul 2018
Edited: Stephen23 on 3 Jul 2018
No loops required, no tricks required, just basic MATLAB indexing:
old = [1 2 3 NaN NaN 0 1 2 NaN 9 8 7 6 NaN NaN NaN 1 1];
idx = ~isnan(old);
new = old(idx | [true,idx(1:end-1)]);
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Mr M. on 3 Jul 2018
Sorry, but this is wrong when old vector starts with NaN values!
Stephen23 on 3 Jul 2018
Edited: Stephen23 on 3 Jul 2018
@Mr M.: you are right. It is easy to fix, just exchange the false for true:
>> old = [NaN,NaN,NaN,1,2,3,NaN,NaN,0,1,2,NaN,9,8,7,6,NaN,NaN,NaN]
old =
NaN NaN NaN 1 2 3 NaN NaN 0 1 2 NaN 9 8 7 6 NaN NaN NaN
>> idx = ~isnan(old);
>> new = old(idx | [true,idx(1:end-1)])
new =
NaN 1 2 3 NaN 0 1 2 NaN 9 8 7 6 NaN

### More Answers (1)

Andrei Bobrov on 2 Jul 2018
a = [1 2 3 NaN NaN 0 1 2 NaN 9 8 7 6 NaN NaN NaN 1 1];
lo = ~isnan(a);
lo(strfind(lo,[0 1])) = true;
out = a(lo);