How to replace the numbers in matrix?

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Han-Yun Chiang
Han-Yun Chiang on 17 Jan 2022
Commented: _ on 18 Jan 2022
Hi,
I'm trying to replace the zeros to the average numbers in between before and after numbers, how to do it?
[1,2,3,0,5,6,0,8,9 ; 1,3,0,0,0,11,13,15,17]
become
[1,2,3,4,5,6,7,8,9 ; 1,3,5,7,9,11,13,15,17]
Thank you
  2 Comments
Han-Yun Chiang
Han-Yun Chiang on 18 Jan 2022
I am so sorry. The second row should be 1,3,5,7,9,11,13,15,17.

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Accepted Answer

_
_ on 18 Jan 2022
Here is a way to do it using linear interpolation on each row. It will interpolate between the non-zero numbers to fill in the zeros (at least two non-zero numbers are required on a given row in order to interpolate) and leave zeros at the beginning or end of the row unchanged. Demonstrated with a slightly more general case:
A = [1,2,3,0,5,6,0,8,9 ; 1,3,0,0,0,11,13,15,17; 0 0 0 0 0 0 0 0 0; 0 0 3 0 0 7 0 0 0]
A = 4×9
1 2 3 0 5 6 0 8 9 1 3 0 0 0 11 13 15 17 0 0 0 0 0 0 0 0 0 0 0 3 0 0 7 0 0 0
c = 1:size(A,2);
for i = 1:size(A,1)
idx = A(i,:) == 0;
if nnz(~idx) < 2
continue
end
A(i,idx) = interp1(c(~idx),A(i,~idx),c(idx),'linear',0);
end
display(A);
A = 4×9
1.0000 2.0000 3.0000 4.0000 5.0000 6.0000 7.0000 8.0000 9.0000 1.0000 3.0000 5.0000 7.0000 9.0000 11.0000 13.0000 15.0000 17.0000 0 0 0 0 0 0 0 0 0 0 0 3.0000 4.3333 5.6667 7.0000 0 0 0
  4 Comments
_
_ on 18 Jan 2022
@Han-Yun Chiang Sorry, I never use "Import Data", so I don't know if there's a way to apply this code when importing data from a file. You may have to just import the data and then run this code on it afterwards.

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More Answers (1)

Adam Danz
Adam Danz on 17 Jan 2022
>I'm trying to replace the zeros to the intermediate numbers
I assume you mean you want to replace 0s with the value immediatly above or below the 0. If the entire columns contains 0s, nothing will change.
A = [1,2,3,0,5,6,0,8,9 ; 1,3,0,0,0,10,12,14,16]
A = 2×9
1 2 3 0 5 6 0 8 9 1 3 0 0 0 10 12 14 16
A(A==0) = A(flipud(A)==0)
A = 2×9
1 2 3 0 5 6 12 8 9 1 3 3 0 5 10 12 14 16
  1 Comment
Han-Yun Chiang
Han-Yun Chiang on 18 Jan 2022
Thank you for your reply.
I made an amendment to express my question more clearly. Please have a look

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