Conditional replacement of array values from another array

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Kevin Su
Kevin Su 2020-4-16
评论： Kevin Su 2020-4-16
Hello,
I'm trying to resolve what I thought would be a simple issue. To simplify the problem, I have two matrices A and B,
I want to write a loop that scans for values in A that are 500 and then replace then in order with the values from B. I tried the included code, but it just didn't work out.
Any help would be appreciated!
A = [500; 500; 40; 50; 500];
B = [20; 30; 60]
for n = 1:5
for m = 1:3
if A(n,1) == 500
A(n,1) = B(m,1);
else
A(n,1) = A(n,1);
end
end
end
%Desired result is A = [20; 30; 40; 50; 60]

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回答（1 个）

Tommy
Tommy 2020-4-16
Do you need a loop?
If you know there are exactly as many 500s in A as there are values in B:
A(A==500) = B;
If there may be more values in B:
A(A==500) = B(1:sum(A==500));
If there may be more 500s in A:
A(find(A==500, numel(B))) = B;
If you can't be sure:
A(find(A==500, numel(B))) = B(1:min(numel(B), sum(A==500)));
  1 个评论
Kevin Su
Kevin Su 2020-4-16
Thanks for such a quick response!
I did not know how many 500s there were in A; I did manage to find a solution; although I'm unsure whether a while loop would be good practice for this.
m = 1;
len = length(B);
while m <= len
for n = 1:5
if A(n,1) == 500
A(n,1) = B(m,1);
m = m + 1;
else
A(n,1) = A(n,1)
end
end
end

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