[R-SIG-Finance] [R-sig-finance] Correct specification for modelling a AR(p)-GJR GARCH(1, 1) - skewed t using fGARCH
bonjourbc9
multeesl at yahoo.co.uk
Tue Sep 1 06:29:06 CEST 2009
Dear All,
while waiting for a reply I tried to tidy up my codes abit and this is what
I used to model a AR(1)-GARCH(1,1) with skewed student t distribution for
the residuals.
>fit1<-garchFit(EMEA~arma(1,0)+ garch(1,1),data=rr.emea ,cond.dist="sstd"
,trace=FALSE)
This is what the fGARCH code returned;
Error Analysis:
Estimate Std. Error t value Pr(>|t|)
mu 0.08031 0.01902 4.223 2.41e-05 ***
ar1 0.09528 0.01835 5.194 2.06e-07 ***
omega 0.03102 0.00890 3.486 0.00049 ***
alpha1 0.10835 0.01399 7.745 9.55e-15 ***
beta1 0.87862 0.01519 57.848 < 2e-16 ***
skew 0.88764 0.02320 38.261 < 2e-16 ***
shape 7.37774 0.90894 8.117 4.44e-16 ***
My question is what is this skew parameter for ?Is it the skewness of the
residuals? or is it the skewness of the standardized residuals??
I tried to extract both the residuals and standardized residuals using the
following code;
>residuals(fit1 , standardize=FALSE)
>residuals(fit1,standardize=TRUE)
When I copy the residuals into excel and calculate its skewness , both
return me negative skewness of -0.5573 ( skew of standardized res) and
-0.85492 (skew of res). So what exactly is the skewness of 0.88764?? I
assume that the shape refers to the shape of the standardized errors?
--
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