Replacing a zero value of a matrix with the value left to it
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Suppose I have a matrix
A =
8 1 6
3 0 7
4 9 2
Now I would like the 0 value to be replaced by the value 3 (the value left of it).
This is an illustrative example for a small matrix. I would like to apply this approach to a much larger matrix
2 Comments
Accepted Answer
Star Strider
on 6 Apr 2022
A = [8 1 6
3 0 7
4 9 2];
A(A==0) = NaN;
B = fillmissing(A,'previous',2) % With Original Matrix
A = [8 1 6
0 0 7
4 9 2];
A(A==0) = NaN;
B = fillmissing(A,'nearest',2) % With Matrix With First Two Rows Being Zero
It would be necessary to use an if block to test for the second condition and then choose the 'nearest' method for that condition. That could go something like this:
A = [8 1 6
0 0 7
4 9 2
5 0 0];
B = A; % Create Result MAtrix
B(B==0) = NaN;
for k = 1:size(A,1)
ixr = find(A(k,:)==0);
if ~isempty(ixr) & any(ixr==1)
B(k,:) = fillmissing(B(k,:),'nearest',2);
elseif ~isempty(ixr) & ~any(ixr==1)
B(k,:) = fillmissing(B(k,:),'previous',2);
end
end
A
B
The loop, and testing each row, seems to me to be the only way to code this, considering that two different interpolation methods are required, depending on the position of the zeros in each row.
.
1 Comment
DGM
on 6 Apr 2022
Edited: DGM
on 6 Apr 2022
Well this is way neater than what I came up with, but I can offer this bit of a modification from what I was doing:
A = [8 1 6
0 3 7 % this row uses 'nearest'
4 9 2
5 0 0];
B = [fliplr(A) A]; % book-matched array
B(B==0) = NaN;
B = fillmissing(B,'previous',2);
B = B(:,size(A,2)+1:end) % trim off excess
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