In the well known matrix form of a least squares regression
where I am trying to solve for B in Y = B1X1 + B2X2 + B3
I might be given X and Y sample data as something like
$X$ = $\begin{bmatrix} 1 & 2 \\ 2 & 3 \\ \end{bmatrix}$
$Y$ = $\begin{bmatrix} 7 \\ 8 \\ \end{bmatrix}$
In such an arrangement how do I include B3? I would think I would want to add it in as always 1 in X
IE
$X$ = $\begin{bmatrix} 1 & 2 \\ 2 & 3 \\ 1 & 1 \\ \end{bmatrix}$
Sorry if the question is not clear.