There are a few typos in the documentation for relist(). I've also
made a few other changes to the file which I believe are
improvements. I've attached a patch against the version under the
'trunk' branch on the svn server checked out today. It was produced by
diff -u /usr/local/src/R/R-svn-trunk/src/library/utils/man/relist.Rd
~/relist-new.Rd
I'd also suggest identical() rather than "==" in the equalities at
the
bottom of the documentation, but that may be overly pedantic.
Dan
--
www.stats.ox.ac.uk/~davison
-------------- next part --------------
--- /usr/local/src/R/R-svn-trunk/src/library/utils/man/relist.Rd 2008-08-16
13:41:50.000000000 +0100
+++ /home/dan/relist-new.Rd 2008-08-16 17:15:54.000000000 +0100
@@ -13,7 +13,7 @@
\alias{is.relistable}
\alias{unlist.relistable}
%
-\title{Allow Re-Listing an unlisted() Object}
+\title{Allow Re-Listing an unlisted Object}
\description{
\code{relist()} is an S3 generic function with a few methods in order
to allow easy inversion of \code{\link{unlist}(obj)} when that is used
@@ -33,8 +33,9 @@
}
\arguments{
- \item{flesh}{ .....}
- \item{skeleton}{ .........}
+ \item{flesh}{a vector to be relisted}
+ \item{skeleton}{a list, the structure of which determines the structure
+ of the result}
\item{x}{an \R object, typically a list (or vector).}
\item{recursive}{logical. Should unlisting be applied to list
components of \code{x}?}
@@ -42,13 +43,13 @@
}
\details{
Some functions need many parameters, which are most easily represented in
- complex structures. Unfortunately, many mathematical functions in \R,
+ nested list structures. Unfortunately, many mathematical functions in \R,
including \code{\link{optim}} and \code{\link{nlm}} can only operate on
functions whose domain is
- a vector. \R has \code{\link{unlist}()} to convert complex objects into a
- vector representation. \code{relist()}, it's methods and the
+ a vector. \R has \code{\link{unlist}()} to convert nested list objects into
a
+ vector representation. \code{relist()}, its methods, and the
functionality mentioned here provide the inverse operation to convert
- vectors back to the convenient structural representation.
+ vectors back to the convenient structured representation.
This allows structured functions (such as \code{optim()}) to have simple
mathematical interfaces.
@@ -60,7 +61,9 @@
list(mean=c(0, 1), vcov=cbind(c(1, 1), c(1, 0))).
}
However, \code{\link{optim}} cannot operate on functions that take lists as
input; it
- only likes numeric vectors. The solution is conversion:
+ only likes numeric vectors. The solution is conversion. Given a
+ function mvdnorm(x, mean, vcov, log=FALSE) which computes the required
+ probability density, then
\preformatted{
ipar <- list(mean=c(0, 1), vcov=cbind(c(1, 1), c(1, 0)))
initial.param <- as.relistable(ipar)
@@ -68,9 +71,8 @@
ll <- function(param.vector)
{
param <- relist(param.vector)
- -sum(dnorm(x, mean = param$mean, vcov = param$vcov,
+ -sum(mvdnorm(x, mean = param$mean, vcov = param$vcov,
log = TRUE))
- ## NB: dnorm() has no vcov... you should get the point
}
optim(unlist(initial.param), ll)
@@ -83,14 +85,14 @@
}
will put the content of flesh on the skeleton. You don't need to specify
skeleton explicitly if the skeleton is stored as an attribute inside flesh.
- In particular, flesh was created from some object obj with
+ In particular, if flesh was created from some object obj with
\code{unlist(as.relistable(obj))}
then the skeleton attribute is automatically set.
As long as \code{skeleton} has the right shape, it should be a precise
inverse
of \code{\link{unlist}}. These equalities hold:
\preformatted{
- relist(unlist(x), skeleton) == x
+ relist(unlist(x), x) == x
unlist(relist(y, skeleton)) == y
x <- as.relistable(x)
