Iterative Outlier Detection
/*--------------------------------------------------------------
SAS Sample Library
Name: ariex07.sas
Description: Example program from SAS/ETS User's Guide,
The ARIMA Procedure
Title: Iterative Outlier Detection
Product: SAS/ETS Software
Keys: time series analysis
PROC: ARIMA
Notes:
--------------------------------------------------------------*/
data airline;
set sashelp.air;
logair = log(air);
if _n_ = 50 then logair = logair - 0.25;
if _n_ >= 100 then logair = logair + 0.5;
run;
/*-- Outlier Detection --*/
proc arima data=airline;
identify var=logair( 1, 12 ) noprint;
estimate q= (1)(12) noint method= ml;
outlier maxnum=3 alpha=0.01;
run;
data airline;
set airline;
if _n_ = 50 then AO = 1;
else AO = 0.0;
if _n_ >= 100 then LS = 1;
else LS = 0.0;
run;
/*-- Airline Model with Outliers --*/
proc arima data=airline;
identify var=logair(1, 12)
crosscorr=( AO(1, 12) LS(1, 12) )
noprint;
estimate q= (1)(12) noint
input=( AO LS )
method=ml plot;
outlier maxnum=3 alpha=0.01;
run;