# Vectorize a double loop

조회 수: 5(최근 30일)
AC 2021년 5월 10일
댓글: Walter Roberson 2021년 5월 13일
Hi everyone
I'm tryng to vectorize the folowing piece of code:
n=30;
d=3;
a=1;
b=2;
cell=3;
for ki = 2:n-1
for kj = 2:n-1
M((cell-1)*n^2+(ki-1)*n+kj,(cell-1)*n^2+(ki-1)*n+kj-1) = 1/d^2;
M((cell-1)*n^2+(ki-1)*n+kj,(cell-1)*n^2+(ki-1)*n+kj) = -4/d^2-a;
M((cell-1)*n^2+(ki-1)*n+kj,(cell-1)*n^2+(ki-1)*n+kj+1) = 1/d^2;
M((cell-1)*n^2+(ki-1)*n+kj,(cell-1)*n^2+(ki-1)*n+kj-n) = 1/d^2;
M((cell-1)*n^2+(ki-1)*n+kj,(cell-1)*n^2+(ki-1)*n+kj+n) = 1/d^2;
C((cell-1)*n^2+(ki-1)*n+kj,1) = b;
end
end
How can I do it? I will appreciate any help! Thanks!
##### 댓글 수: 3표시숨기기 이전 댓글 수: 2
Walter Roberson 2021년 5월 13일
If you feel that your post is unclear, then since you are the one who wrote it, you should clarify it.

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### 답변(1개)

Bob Thompson 2021년 5월 10일
Does this work? I haven't been able to test it.
M((cell-1)*n^2+(1:n-2)*n+(2:n-1),(cell-1)*n^2+(1:n-2)*n+(2:n-1)-1) = 1/d^2;
M((cell-1)*n^2+(1:n-2)*n+(2:n-1),(cell-1)*n^2+(1:n-2)*n+(2:n-1)) = -4/d^2-a;
M((cell-1)*n^2+(1:n-2)*n+(2:n-1),(cell-1)*n^2+(1:n-2)*n+(2:n-1)+1) = 1/d^2;
M((cell-1)*n^2+(1:n-2)*n+(2:n-1),(cell-1)*n^2+(1:n-2)*n+(2:n-1)-n) = 1/d^2;
M((cell-1)*n^2+(1:n-2)*n+(2:n-1)j,(cell-1)*n^2+(1:n-2)*n+(2:n-1)+n) = 1/d^2;
C((cell-1)*n^2+(1:n-2)*n+(2:n-1),1) = b;
##### 댓글 수: 1표시숨기기 없음
AC 2021년 5월 10일
Thank you for your answer! I tried this, but didn't work. When using the double for loop, I get (n-2)*(n-2) combinations of ki's and kj's. But (cell-1)*n^2+(1:n-2)*n+(2:n-1) is a vector of length (n-2). I need a vector of length (n-2)*(n-2)

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R2020a

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