\name{RcppExample}
\alias{RcppExample}
\alias{print.RcppExample}
\title{Rcpp R / C++ interface example}
\description{
  \code{RcppExample} illustrates how the \code{Rcpp} R/C++
  interface class library is used.
}
\usage{
RcppExample(params, nlist, numvec, nummat, df, datevec, stringvec,
fnvec, fnlist)
\method{print}{RcppExample}(x,...)
}
\arguments{
  \item{params}{A heterogeneous list specifying \code{method} (string),
    \code{tolerance} (double), \code{maxIter} (int).}
  \item{nlist}{a list of named numeric values (double or int).}
  \item{numvec}{a numeric 1D vector (double or int).}
  \item{nummat}{a numeric 2D matrix (double or int).}
  \item{df}{a data frame.}
  \item{datevec}{a vector of Date's.}
  \item{stringvec}{a vector of strings.}
  \item{fnvec}{an R function with numeric vector argument.}
  \item{fnlist}{an R function with list argument.}
  \item{x}{Object of type \code{RcppExample}.}
  \item{...}{Extra named parameters.}
  }
\details{

  The C++ represention of data frames are not passed back to R in a form
  that R recognizes as a data frame, but it is a simple matter to do the
  conversion. For example, the return value named \code{PreDF} (see
  return values below) is not seen as a data frame on the R side (thus
  the name "pre-data frame"), but it can be converted to a data frame
  using \code{df <- data.frame(result$PreDF)}.
  
  The print.RcppExample() function is defined so that we can control
  what gets printed when a variable assigned the return value is entered
  on a line by itself. It is defined to simply list the names of the
  fields returned (see RcppExample.R).

  The source files for this
  example and for the \code{Rcpp} class library
  can be found in the RcppTemplate package source archive (the .tar.gz file).
}
\value{
  \code{RcppExample} returns a list containing:
  \item{method}{string input paramter}
  \item{tolerance}{double input paramter}
  \item{maxIter}{int input parameter}
  \item{nlFirstName}{first name in nlist}
  \item{nlFirstValue}{first value in nlist}
  \item{matD}{R matrix from an RcppMatrix<double> object}
  \item{stlvec}{R vector from a vector<double> object}
  \item{stlmat}{R matrix from a vector<vector<double> > object}
  \item{a}{R matrix from C/C++ matrix}
  \item{v}{R vector from C/C++ vector}
  \item{strings}{R vector of strings from vector<string> object}
  \item{InputDF}{a data frame passed in from R}
  \item{PreDF}{a data frame created on C++ side to be passed back to R}
  \item{params}{input parameter list (this is redundant because we returned the input parameters above)}
  }

\author{Dominick Samperi wrote most of Rcpp during 2005 and 2006.  Dirk
  Eddelbuettel made some additions, and became maintainer in 2008.}

\references{
  Samperi, D., (2006) \emph{Rcpp: R/C++ Interface Classes:
      Using C++ Libraries from R},
    available as a package vignette, or in the \code{RcppTemplate}
    package \code{doc} subdirectory
  (\code{RcppAPI.pdf}).
    
  \emph{Writing R Extensions}, available at \url{http:www.r-project.org}.
}
\examples{

params <- list(method='BFGS',
               tolerance=1.0e-8,
               maxIter=1000,
               startDate=as.Date('2006-7-15'))

nlist <- list(ibm = 80.50, hp = 53.64, c = 45.41)

numvec <- seq(1,5) # numerical vector

nummat <- matrix(seq(1,20),4,5) # numerical matrix

stringvec <- c("hello", "world", "fractal") # string vector

datestr <- c('2006-6-10', '2006-7-12', '2006-8-10')
datevec <- as.Date(datestr, "\%Y-\%m-\%d") # date vector

df <- data.frame(a=c(TRUE, TRUE, FALSE), b=I(c('a','b','c')),
c=c('beta', 'beta', 'gamma'), dates=datevec)

fnvec <- function(x) { sum(x) } # Add up components of vector

fnlist <- function(l) { # Return vector with 1 added to each component
  vec <- c(l$alpha + 1, l$beta + 1, l$gamma + 1)
  vec
}

result <- RcppExample(params, nlist, numvec, nummat, df, datevec,
                      stringvec, fnvec, fnlist)

result

}

\keyword{programming}
\keyword{interface}