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 <spencer.graves@pdf.com> 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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