In matrix notation what does it mean X 'X
I see it in this academic paper, I can't find it in matrix operation and can't search with google.
http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2400219
page 7 , paragraph 3.1
[Math] In Matrix notation what does it mean X ‘X
notation
Related Solutions
It looks like he means a matrix when he uses double bars:
He uses the standard notation for a determinant, i.e. single bars:
I don't know if his notation for matrices was something that was common at the time he wrote the book, but I don't think it's popular now.
In section 2, the paper gives this definition:
Best Answer
$X'$ is the transpose matrix and $X'X$ is the product the same matrix. exemple $$X=\left(\matrix{1 & 2&4\\1&3&5}\right),$$ then, $$X'X=\left(\matrix{1 & 1\\2&3\\4&5}\right)\left(\matrix{1 & 2&4\\1&3&5}\right).$$