Fill NaN cells using surrounding data values

2011 8 3
3 个回答
回答已采纳
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0 个投票

Hi,
I would like to fill NaN cells in the rows of a matrix with the mean of the immediately surrounding values.
For example I would like to convert
>> A=magic(5);
>> A(:,2:4)=NaN;
>> A(1:2,:)=NaN;
>> A
A =
NaN NaN NaN NaN NaN
NaN NaN NaN NaN NaN
4 NaN NaN NaN 22
10 NaN NaN NaN 3
11 NaN NaN NaN 9
>>
To this:
>> A
A =
NaN NaN NaN NaN NaN
NaN NaN NaN NaN NaN
4.0000 13.0000 13.0000 13.0000 22.0000
10.0000 6.5000 6.5000 6.5000 3.0000
11.0000 10.0000 10.0000 10.0000 9.0000
>>
Only converting those NaN cells that are surrounded on the row by non-NaN values.
I hope this is clear.
Thanks very much

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Walter Roberson
Walter Roberson 2011-8-3

0 个投票

You may wish to see John's MATLAB File Exchange contribution inpaint_nans

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James
James 2011-8-3
This looks like it might do the trick, I will give it a shot.
Thanks

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更多回答（2 个）

Image Analyst
Image Analyst 2011-8-3

0 个投票

It can't be that hard - did you know there is an "isnan()" function, as well as mean() and sum()? Give it a shot yourself first - it's not hard.
James
James 2011-8-3

0 个投票

Sure, let me preface this with the comment that I am definitely a beginner MATLAB user.
I can solve the example that I gave above (in probably a very round about way) with the following:
b=sum(~isnan(A)')'>0;%Find Rows where there are non-NaN values
c= sum(isnan(A(b,:)))>0; %in those rows find the NaN values
d=mean(A(b,~c)')'; %Find the mean of the entire rows identified in c
A(b,c)= repmat(d,1,sum(c)) %Fill in the appropriate cells
Where I am getting stuck is:
Firstly: Taking the mean of only the adjacent cells in the row rather than the whole row
Secondly: Only replacing NaN values where they are surrounded on both sides with non-NaN values
i.e. A =
NaN NaN NaN NaN NaN NaN NaN
NaN NaN NaN NaN NaN NaN NaN
NaN 6 NaN NaN NaN NaN NaN
5 14 NaN NaN NaN 36 NaN
13 15 NaN NaN NaN 44 4
21 NaN NaN NaN NaN 3 12
22 31 NaN NaN NaN 11 20
>>
to
A =
NaN NaN NaN NaN NaN NaN NaN
NaN NaN NaN NaN NaN NaN NaN
NaN 6.0000 NaN NaN NaN NaN NaN
5.0000 14.0000 25.0000 25.0000 25.0000 36.0000 NaN
13.0000 15.0000 29.5000 29.5000 29.5000 44.0000 4.0000
21.0000 12.0000 12.0000 12.0000 12.0000 3.0000 12.0000
22.0000 31.0000 21.0000 21.0000 21.0000 11.0000 20.0000
>>
Thanks Again

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