inv(A) versus /A. Which of the two is the correct one

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ektor
ektor 2015-2-12
评论： Stephen23 2015-2-13
Hi all,
Let B be a n by 2 matrix and A is a 2 by 2 positive definite matrix. Which of the following two is correct
for i=1:n
B(i,:)*inv(A)*B(i,:)';
end
or
for i=1:n
(B(i,:)/A)*B(i,:)';
end
Best, Stef

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回答（1 个）

Matt J
Matt J 2015-2-12
Both are equivalent. For large matrices the 2nd would be more efficient.
Further efficiency would be gained by vectorizing. The whole loop is just,
sum( (B/A).*B, 2)

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