[R-SIG-Finance] copula-based higher moment optimization
Brian G. Peterson
brian at braverock.com
Sun Oct 7 14:26:13 CEST 2007
Alexander Moreno wrote:
> Is there any very quick and dirty way to do a copula-based optimization
> incorporating skewness using R packages, i.e. something that's close to
> being automated? Any help would be appreciated.
Is there a particular paper that you're trying to emulate?
Here's the simple answer: there is no "automated" portfolio optimizer
for higher moments in R.
Here's the complicated answer: there are many copula functions in R that
could be used for a better estimate of the moments of your distribution,
and those moments could be fed into an optimization routine. There are
also many non-copula methods in R for fitting non-normal distributions
for a good estimate of the higher moments of the distribution (or, more
appropriately, for a good estimate of the risk metrics at a particular
quantile or confidence level).
Probably the "simplest" (most-automated) copula-based method for
portfolio optimization in R that I've seen was done by some of Prof.
Wuertz's graduate students, who were working on fitting a copula to the
tail of the distribution to get a better estimate of Expected Shortfall,
and then using that to build ES-optimal portfolios. I assume that Prof.
Wuertz's team work will end up in RMetrics eventually, but I don't
believe it's made it into the released code just yet: check the
examples, tests, and documentation for the fCopula package to find out.
You can also use a Cornish Fisher expansion to calculate a four-moment
VaR (see package PerformanceAnalytics) and use that as the downside risk
metric in your optimization.
Regards,
- Brian
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