# How to find closest values within a matirx

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A on 29 Apr 2022
Commented: A on 30 Apr 2022
Hi have a matirx
[NAN NAN NAN 7 8 9;
NAN NAN 5 7 8 7;
4 8 6 8 3 4;
4 7 0 1 1 4]
How do I replace the NAN values with the closest values known values. So the matirx will kind of look like
[4 5 7 7 8 9;
4 8 5 7 8 7;
4 8 6 8 3 4;
4 7 0 1 1 4]
A on 29 Apr 2022
Yea it kinda like that logic, like nearest neighbors almost. Becasue for (2,2) the values is close is (3,2) rather than (2,3)

Matt J on 29 Apr 2022
A=[nan(1,3) 7 8 9;
nan(1,2) 5 7 8 7;
4 8 6 8 3 4;
4 7 0 1 1 4]
A = 4×6
NaN NaN NaN 7 8 9 NaN NaN 5 7 8 7 4 8 6 8 3 4 4 7 0 1 1 4
nanmap=isnan(A);
[~,idx]=bwdist(~nanmap);
A(nanmap)=A(idx(nanmap))
A = 4×6
4 5 5 7 8 9 4 8 5 7 8 7 4 8 6 8 3 4 4 7 0 1 1 4
A on 30 Apr 2022
That makes more sense, thank you!!

DGM on 29 Apr 2022
Edited: DGM on 29 Apr 2022
I'm not really sure what you mean by "closest values". Maybe you're talking about inpainting?
A = [NaN NaN NaN 7 8 9;
NaN NaN 5 7 8 7;
4 8 6 8 3 4;
4 7 0 1 1 4]
A = 4×6
NaN NaN NaN 7 8 9 NaN NaN 5 7 8 7 4 8 6 8 3 4 4 7 0 1 1 4
B = regionfill(A,isnan(A))
B = 4×6
5.4778 5.8000 5.9333 7.0000 8.0000 9.0000 5.1556 5.9889 5.0000 7.0000 8.0000 7.0000 4.0000 8.0000 6.0000 8.0000 3.0000 4.0000 4.0000 7.0000 0 1.0000 1.0000 4.0000
If you don't have regionfill() (Image Processing Toolbox), you can always use John's inpaint_nans() on the File Exchange
C = inpaint_nans(A)
You might also be able to use fillmissing() depending on the directional behavior you intend.
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DGM on 29 Apr 2022
Then Matt's answer might be more what you want