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

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

[Stephen23]

Don't use a loop, learn to vectorize your code. Matt J's answer shows this.

Answer 1

[Matt J]

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)