Rcpp (version 0.7.7)

RcppExample: Rcpp R / C++ interface example

Description

RcppExample illustrates how the Rcpp R/C++ interface class library is used.

Usage

RcppExample(params, nlist, numvec, nummat, df, datevec, stringvec,
fnvec, fnlist)
## S3 method for class 'RcppExample':
print(x,...)

Arguments

params

A heterogeneous list specifying method (string), tolerance (double), maxIter (int).

nlist

a list of named numeric values (double or int).

numvec

a numeric 1D vector (double or int).

nummat

a numeric 2D matrix (double or int).

df

a data frame.

datevec

a vector of Date's.

stringvec

a vector of strings.

fnvec

an R function with numeric vector argument.

fnlist

an R function with list argument.

x

Object of type RcppExample.

...

Extra named parameters.

Value

• RcppExample returns a list containing:
• method
  string input paramter
• tolerance
  double input paramter
• maxIter
  int input parameter
• nlFirstName
  first name in nlist
• nlFirstValue
  first value in nlist
• matD
  R matrix from an RcppMatrix object
• stlvec
  R vector from a vector object
• stlmat
  R matrix from a vector > object
• a
  R matrix from C/C++ matrix
• v
  R vector from C/C++ vector
• strings
  R vector of strings from vector object
• InputDF
  a data frame passed in from R
• PreDF
  a data frame created on C++ side to be passed back to R
• params
  input parameter list (this is redundant because we returned the input parameters above)

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 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 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 Rcpp class library can be found in the RcppTemplate package source archive (the .tar.gz file).

References

Samperi, D., (2006) Rcpp: R/C++ Interface Classes: Using C++ Libraries from R, available as a package vignette, or in the RcppTemplate package doc subdirectory (RcppAPI.pdf). Writing R Extensions, available at 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