Spencer, how about something like this:
archTest=function (x, lags= 16){
#x is a vector
require(vars)
s=embed(x,lags)
y=VAR(s,p=1,type="const")
result=arch(y,multi=F)$arch.uni[[1]]
return(result)
}
can you, or maybe Bernhard, check and see whether this function gives the
correct result?
thanks,
On 2/1/08, Spencer Graves <[EMAIL PROTECTED]> wrote:
>
> Hi, Tom:
>
> The 'arch' function in the 'vars' package is supposed to be able
> to do that. Unfortunately, I was unable to make it work for a
> univariate series. Bernhard Pfaff, the author of 'vars', said that if I
> read the code for 'arch', I could easily retrieve the necessary lines
> and put them in my own function; I have not so far found the time to
> try that. If you do, or if you get a better answer than this, would you
> please let me know? I would like to have this capability for the
> 'FinTS' package, and I would happily write a help page if someone would
> contribute the function -- or use a function in another package. Tsay
> (2005) Analysis of Financial Time Series, 2nd ed. (Wiley) includes an
> example on p. 103 that could be used for a reference.
>
> Hope this helps.
> Spencer Graves
>
> tom soyer wrote:
> > Hi,
> >
> > Does anyone know if R has a Lagrange multiplier (LM) test for ARCH
> > effects for univariant time series?
> >
> > Thanks!
> >
> >
>
--
Tom
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