# returns the variable (or matrix), lagged from 1 to p times,
# with the first p rows filled with ones (to avoid divide errors)
# remember to drop those rows before doing analysis
function lagged_x = lags(x,p)
	k = columns(x);
	lagged_x = lag(x,1);
	if p > 1
		for i = 2:p
			lagged_x = [lagged_x, lag(x,i)]; 
		endfor
	endif	
endfunction