The VARMAX Procedure |
The following are examples of syntax for model fitting:
/* Data 'a' Generated Process */ proc iml; sig = {1.0 0.5, 0.5 1.25}; phi = {1.2 -0.5, 0.6 0.3}; call varmasim(y,phi) sigma = sig n = 100 seed = 46859; cn = {'y1' 'y2'}; create a from y[colname=cn]; append from y; run;;
/* when the series has a linear trend */ proc varmax data=a; model y1 y2 / p=1 trend=linear; run; /* Fit subset of AR order 1 and 3 */ proc varmax data=a; model y1 y2 / p=(1,3); run; /* Check if the series is nonstationary */ proc varmax data=a; model y1 y2 / p=1 dftest print=(roots); run; /* Fit VAR(1) in differencing */ proc varmax data=a; model y1 y2 / p=1 print=(roots) dify=(1); run; /* Fit VAR(1) in seasonal differencing */ proc varmax data=a; model y1 y2 / p=1 dify=(4) lagmax=5; run; /* Fit VAR(1) in both regular and seasonal differencing */ proc varmax data=a; model y1 y2 / p=1 dify=(1,4) lagmax=5; run; /* Fit VAR(1) in different differencing */ proc varmax data=a; model y1 y2 / p=1 dif=(y1(1,4) y2(1)) lagmax=5; run; /* Options related to prediction */ proc varmax data=a; model y1 y2 / p=1 lagmax=3 print=(impulse covpe(5) decompose(5)); run; /* Options related to tentative order selection */ proc varmax data=a; model y1 y2 / p=1 lagmax=5 minic print=(parcoef pcancorr pcorr); run; /* Automatic selection of the AR order */ proc varmax data=a; model y1 y2 / minic=(type=aic p=5); run; /* Compare results of LS and Yule-Walker Estimators */ proc varmax data=a; model y1 y2 / p=1 print=(yw); run; /* BVAR(1) of the nonstationary series y1 and y2 */ proc varmax data=a; model y1 y2 / p=1 prior=(lambda=1 theta=0.2 ivar); run; /* BVAR(1) of the nonstationary series y1 */ proc varmax data=a; model y1 y2 / p=1 prior=(lambda=0.1 theta=0.15 ivar=(y1)); run;
/* Data 'b' Generated Process */ proc iml; sig = { 0.5 0.14 -0.08 -0.03, 0.14 0.71 0.16 0.1, -0.08 0.16 0.65 0.23, -0.03 0.1 0.23 0.16}; sig = sig * 0.0001; phi = {1.2 -0.5 0. 0.1, 0.6 0.3 -0.2 0.5, 0.4 0. -0.2 0.1, -1.0 0.2 0.7 -0.2}; call varmasim(y,phi) sigma = sig n = 100 seed = 32567; cn = {'y1' 'y2' 'y3' 'y4'}; create b from y[colname=cn]; append from y; quit;
/* Cointegration Rank Test using Trace statistics */ proc varmax data=b; model y1-y4 / p=2 lagmax=4 cointtest; run; /* Cointegration Rank Test using Max statistics */ proc varmax data=b; model y1-y4 / p=2 lagmax=4 cointtest=(johansen=(type=max)); run; /* Common Trends Test using Filter(Differencing) statistics */ proc varmax data=b; model y1-y4 / p=2 lagmax=4 cointtest=(sw); run; /* Common Trends Test using Filter(Residual) statistics */ proc varmax data=b; model y1-y4 / p=2 lagmax=4 cointtest=(sw=(type=filtres lag=1)); run; /* Common Trends Test using Kernel statistics */ proc varmax data=b; model y1-y4 / p=2 lagmax=4 cointtest=(sw=(type=kernel lag=1)); run; /* Cointegration Rank Test for I(2) */ proc varmax data=b; model y1-y4 / p=2 lagmax=4 cointtest=(johansen=(iorder=2)); run; /* Fit VECM(2) with rank=3 */ proc varmax data=b; model y1-y4 / p=2 lagmax=4 print=(roots iarr) ecm=(rank=3 normalize=y1); run;
/* Weak Exogenous Testing for each variable */ proc varmax data=b outstat=bbb; model y1-y4 / p=2 lagmax=4 ecm=(rank=3 normalize=y1); cointeg rank=3 exogeneity; run; /* Hypotheses Testing for long-run and adjustment parameter */ proc varmax data=b outstat=bbb; model y1-y4 / p=2 lagmax=4 ecm=(rank=3 normalize=y1); cointeg rank=3 normalize=y1 h=(1 0 0, 0 1 0, -1 0 0, 0 0 1) j=(1 0 0, 0 1 0, 0 0 1, 0 0 0); run; /* ordinary regression model */ proc varmax data=grunfeld; model y1 y2 = x1-x3; run; /* Ordinary regression model with subset lagged terms */ proc varmax data=grunfeld; model y1 y2 = x1 / xlag=(1,3); run; /* VARX(1,1) with no current time Exogenous Variables */ proc varmax data=grunfeld; model y1 y2 = x1 / p=1 xlag=1 nocurrentx; run; /* VARX(1,1) with different Exogenous Variables */ proc varmax data=grunfeld; model y1 = x3, y2 = x1 x2 / p=1 xlag=1; run; /* VARX(1,2) in difference with current Exogenous Variables */ proc varmax data=grunfeld; model y1 y2 = x1 / p=1 xlag=2 difx=(1) dify=(1); run;
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