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modelarima
2003 Nov 24
0
link between arima and arma fit
Hi dear sirs,
I am wondering why the fit of the time serie x with an arima and the fit of
diff(x) with an arma (same coeff p & d) differ one from another
here are the output of R:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> modelarma<-arma(diff(x),c(7,5))
> modelarma
Call:
arma(x = diff(x), order = c(7, 5))
Coefficient(s):
ar1 ar2 ar3 ar4 ar5 ar6 ar7 ma1 ma2
0.06078 -0.44774 0.41881 0.47624 0.01406 0.06565 -0.06167 -0.01294 0.31313
ma3 ma4 ma5 intercept
-0.49027 -0.55461 -0.11520 -0.10692
> modelarima<-arima(x,c...