How to replace the numbers in matrix?

Question

Han-Yun Chiang 2022-1-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1630730-how-to-replace-the-numbers-in-matrix

评论： Voss 2022-1-18

采纳的回答： Voss

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

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Adam Danz 2022-1-18

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 2022-1-18

I am so sorry. The second row should be 1,3,5,7,9,11,13,15,17.

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Answer 1

Voss 2022-1-18

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在 MATLAB Online 中打开

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

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Han-Yun Chiang 2022-1-18

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 2022-1-18

@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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Answer 2

Adam Danz 2022-1-17

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https://ww2.mathworks.cn/matlabcentral/answers/1630730-how-to-replace-the-numbers-in-matrix#answer_876300

在 MATLAB Online 中打开

>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