How to replace the numbers in matrix?

11 views (last 30 days)
Han-Yun Chiang
Han-Yun Chiang on 17 Jan 2022
Commented: Voss 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
Adam Danz
Adam Danz on 18 Jan 2022
In the updated question, it's not clear how the first two rows below become the last two rows. It looks like you're taking the average in some cases but it's not clear what happens when there are consecutive 0s. Please explain the conversion rule(s).
1 2 3 0 5 6 0 8 9
1 3 0 0 0 10 12 14 16
1 2 3 4 5 6 7 8 9
1 3 5 7 9 10 12 14 16
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.

Sign in to comment.

Accepted Answer

Voss
Voss 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
Han-Yun Chiang
Han-Yun Chiang on 18 Jan 2022
Done!
It works when I typed in the data in the script, however, I couldn't apply it to the import data (numeric matrix form). Do you know how to amened it ?
Voss
Voss 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.

Sign in to comment.

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

Sign in to comment.

Categories

Find more on Data Import from MATLAB in Help Center and File Exchange

Tags

Products


Release

R2021a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!