# How to Use the commonsMath Package

#### David B. Dahl

## Overview

The commonsMath package provides access to the Apache Commons Mathematics Library. It can can accessed via the:

- rscala package, or
- rJava package.

We demonstrate below how to use it in:

- R scripts, or
- R packages

## Usage in R Scripts

#### Access via rscala

    library("rscala")
    s <- scala("commonsMath")
    rng1 <- s$.new_org.apache.commons.math3.random.RandomDataGenerator()
    rng1$reSeed(7342L)
    rng1$nextGaussian(0,1)

    ## [1] -1.167763

#### Access via rJava

    library("rJava")
    .jinit(Sys.glob(file.path(system.file(package="commonsMath"), "java", "*.jar")))
    rng2 <- .jnew("org.apache.commons.math3.random.RandomDataGenerator")
    rng2$reSeed(.jlong(7342L))
    rng2$nextGaussian(0,1)

    ## [1] -1.167763

## Usage in R Packages

#### Access via rscala

The `DESCRIPTION` should have `Imports: rscala, commonsMath`.

The `NAMESPACE` should have `import(rscala)`.

Define an `.onLoad` function like the following:

    .onLoad <- function(libname, pkgname) {
      s <- scala("commonsMath")
      assign("s", s, envir = parent.env(environment()))
    }

Package functions can then assess classes and methods from the commonsMath package, e.g.:

    rstdnorm <- function() {
      rng1 <- s$.new_org.apache.commons.math3.random.RandomDataGenerator()
      rng1$nextGaussian(0.0,1.0)
    }

#### Access via rJava

The `DESCRIPTION` should have `Imports: rJava, commonsMath`.

The `NAMESPACE` should first have `import(rscala)` and then have `import(commonsMath)`.

Define an `.onLoad` function like the following:

    .onLoad <- function(libname, pkgname) {
      .jpackage(pkgname, lib.loc=libname)
    }

Package functions can then assess classes and methods from the commonsMath package, e.g.:

    rstdnorm <- function() {
      rng2 <- .jnew("org.apache.commons.math3.random.RandomDataGenerator")
      rng2$nextGaussian(0,1)
    }