regarding 6.91 in page 182 of the book,
"Hence, x is a linear transformation of y, and we obtain",
in the final part of the line right below, on the right of Sigma:
we seem to be taking the transpose of (A^T A)^-1 A^T ,
and wouldn't that give us: A (A^T A)^-1 applying that the transpose of the inverse is the inverse of the transpose?
instead what I see is A(A^T A)^-1 (as if part of it was transposed but not the whole of it)
unless we are considering that A^T A was calculated fully in which case the result would be in any case the same
thank you for clarifying and congrats for a great book
regarding 6.91 in page 182 of the book, "Hence, x is a linear transformation of y, and we obtain",
in the final part of the line right below, on the right of Sigma:
we seem to be taking the transpose of (A^T A)^-1 A^T , and wouldn't that give us: A (A^T A)^-1 applying that the transpose of the inverse is the inverse of the transpose?
instead what I see is A(A^T A)^-1 (as if part of it was transposed but not the whole of it)
unless we are considering that A^T A was calculated fully in which case the result would be in any case the same
thank you for clarifying and congrats for a great book