Rcpp demo for BioC2014

rcpp.R

# Rcpp demo
# Mike Love
# BioC2014
# 30 Jul 2014


# Go here for all the info:
# http://dirk.eddelbuettel.com/code/rcpp.html
# examples: go down to the 'Other documentation' vignettes

library(Rcpp)
library(inline)

f1 <- cxxfunction(
  signature(xx = "integer", yy = "numeric" ),
'int x = as<int>(xx);
double y = as<double>(yy);
double z = x * y;
return wrap(z);',
  plugin = "Rcpp" )

f1(10, 4.4)


############################################


# use Rcpp numeric vectors and sugar
# http://dirk.eddelbuettel.com/code/rcpp/Rcpp-sugar.pdf

f2 <- cxxfunction(
  signature(xx = "numeric", yy = "numeric" ),
'Rcpp::NumericVector x(xx);
Rcpp::NumericVector y(yy);
Rcpp::NumericVector m = x * y;
Rcpp::NumericVector a = x + y;
return Rcpp::List::create(Rcpp::Named("multiply") = m,
                          Rcpp::Named("add") = a);',
  plugin = "Rcpp" )

f2(1:5, 6:10)

############################################

# Armadillo C++ linear algebra library
# for nice looking matrix multiplication
# http://cran.r-project.org/web/packages/RcppArmadillo/vignettes/RcppArmadillo-intro.pdf
# The library documention is here: http://arma.sourceforge.net/docs.html
# I'm not sure the status of converting back and forth between arma objects and Rcpp 

library(RcppArmadillo)

f3 <- cxxfunction(
  signature(xx = "numeric", yy = "numeric" ),
'arma::mat x = Rcpp::as<arma::mat>(xx);
arma::mat y = Rcpp::as<arma::mat>(yy);
arma::mat m = x * y;
arma::mat s = sqrt(x);
return Rcpp::List::create(Rcpp::Named("multiply") = m,
                          Rcpp::Named("sqrt") = s);',
  plugin = "RcppArmadillo" )

(xx <- matrix(1:6,ncol=2))
(yy <- matrix(1:8,ncol=4))

dim(xx)
dim(yy)

f3(xx,yy)