> What is the constant supposed to do or be? > How does it fit into the regression equation?- Hide quoted text -
Here's how Ivo Welch describes the use of the constant:
"Most of the time, the user will provide a constant ('1') as x(0) for each observation in order to allow the regression package to fit an intercept."
Also, his code is an implementation of the Gentleman algorithm, if that helps you to understand what he's doing:
W. M. Gentleman, University of Waterloo, "Basic Description For Large, Sparse Or Weighted Linear Least Squares Problems (Algorithm AS 75)," Applied Statistics (1974) Vol 23; No. 3