After deciding you had no non-stationarity I ran this model suggested by MINIC and SCAN (a ma and ar of 1)
proc arima data= tsdata;
identify var=spend scan esacf minic;
ESTIMATE p=(1) q=(1);
run;
ods graphics off;
when I ran this I got the following warning which I have never encountered in ARIMA.
Warning: The model defined by the new estimates is unstable. The iteration process has been terminated.
Warning: Estimates may not have converged.
Any suggestions? I have 50 data points if that matters.
proc arima data= tsdata;
identify var=spend scan esacf minic;
ESTIMATE p=(1) q=(1);
run;
ods graphics off;
when I ran this I got the following warning which I have never encountered in ARIMA.
Warning: The model defined by the new estimates is unstable. The iteration process has been terminated.
Warning: Estimates may not have converged.
Any suggestions? I have 50 data points if that matters.