How to find closest values within a matirx

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A
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]
  4 Comments
Steven Lord
Steven Lord on 29 Apr 2022
What are your rules for "closest"? For element (1, 3) you fill in the NaN with the value from (1, 4) rather than the value from (2, 3). But for element (2, 2) you fill in with the value from (3, 2) rather than the value from (2, 3). Why do you choose the element to the side in the first case but the element below in the second?
A
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)

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Accepted Answer

Matt J
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

More Answers (1)

DGM
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.
  2 Comments
A
A on 29 Apr 2022
No like creating new values, kind of like subsituing the already known values into the NAN. So kinda like nearest neighbor, if we know what its closes elements are then we subisite them into the NAN
DGM
DGM on 29 Apr 2022
Then Matt's answer might be more what you want

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