cppFunction: Define an R Function with a C++ Implementation

In Rcpp: Seamless R and C++ Integration

Define an R Function with a C++ Implementation

Description

Dynamically define an R function with C++ source code. Compiles and links a shared library with bindings to the C++ function then defines an R function that uses .Call to invoke the library.

Usage

cppFunction(code, depends = character(), plugins = character(), includes = character(),
            env = parent.frame(), rebuild = FALSE, cacheDir = getOption("rcpp.cache.dir",
            tempdir()), showOutput = verbose, verbose = getOption("verbose"), echo = TRUE)

Arguments

code	Source code for the function definition.
depends	Character vector of packages that the compilation depends on. Each package listed will first be queried for an inline plugin to determine header files to include. If no plugin is defined for the package then a header file based the package's name (e.g. PkgName.h) will be included.
plugins	Character vector of inline plugins to use for the compilation.
includes	Character vector of user includes (inserted after the includes provided by depends).
env	The environment in which to define the R function. May be NULL in which case the defined function can be obtained from the return value of cppFunction.
rebuild	Force a rebuild of the shared library.
cacheDir	Directory to use for caching shared libraries. If the underlying code passed to sourceCpp has not changed since the last invocation then a cached version of the shared library is used. The default value of tempdir() results in the cache being valid only for the current R session. Pass an alternate directory to preserve the cache across R sessions.
showOutput	TRUE to print R CMD SHLIB output to the console.
verbose	TRUE to print detailed information about generated code to the console.
echo	TRUE to silence output from optional R evaluation if set to FALSE.

Details

Functions defined using cppFunction must have return types that are compatible with Rcpp::wrap and parameter types that are compatible with Rcpp::as.

The shared library will not be rebuilt if the underlying code has not changed since the last compilation.

Value

An R function that uses .Call to invoke the underlying C++ function.

Note

You can also define R functions with C++ implementations using the sourceCpp function, which allows you to separate the C++ code into it's own source file. For many use cases this is an easier and more maintainable approach.

See Also

sourceCpp, evalCpp

Examples

## Not run: 

cppFunction(
    'int fibonacci(const int x) {
        if (x == 0) return(0);
        if (x == 1) return(1);
        return (fibonacci(x - 1)) + fibonacci(x - 2);
    }')

cppFunction(depends = "RcppArmadillo",
    'List fastLm(NumericVector yr, NumericMatrix Xr) {

        int n = Xr.nrow(), k = Xr.ncol();

        arma::mat X(Xr.begin(), n, k, false);
        arma::colvec y(yr.begin(), yr.size(), false);

        arma::colvec coef = arma::solve(X, y);
        arma::colvec resid = y - X*coef;

        double sig2 = arma::as_scalar(arma::trans(resid)*resid/(n-k) );
        arma::colvec stderrest = arma::sqrt(
            sig2 * arma::diagvec(arma::inv(arma::trans(X)*X)));

        return List::create(Named("coefficients") = coef,
            Named("stderr")       = stderrest
        );
    }')

cppFunction(plugins=c("cpp11"), '
    int useCpp11() {
        auto x = 10;
        return x;
    }')


## End(Not run)

Rcpp documentation built on Nov. 3, 2024, 1:06 a.m.