Why is x hat in the row space? I understand why e is in the left nullspace, I understand why p is in the column space, I get why the nullspace is 0 (given indpendepent columns), but I dont understand why x hat is in the rowspace...
The problem is as follows: Which of the four subspaces contains the error vector e? Which contains p? Which contains xˆ? What is the nullspace of A? This is all regarding a least squares projection where p is the projected vector, e is error vector, and x hat is the vector in which Axhat = p.