=SET NOECHO
PROC QR
** INPUTS: X_ N_ K_
** OUTPUTS: Q_ R_
** IMPORTANT: THIS CALLS THE HH PROC WHICH MUST BE PRELOADED
* compute the P matrix for the first column
matrix Q_=IDEN(N_)
matrix R_=X_
DO #=1,K_
gen1 fr_=N_+1-#
copy R_ a_ / frow=#;N_ fcol=#;# trow=1;fr_ tcol=1;1
exec HH
?del a_
* save it as P#_
matrix P#_=P_
*print P#_
matrix P_=IDEN(N_)
copy P#_ P_ / frow=1;fr_ fcol=1;fr_ trow=#;N_ tcol=#;N_
matrix Q_=Q_*P_
matrix R_=P_*R_
* get the bottom of the second column of PX
ENDO
* check it
print Q_ R_
matrix check_=Q_*R_
print check_
PROCEND
=SET ECHO