mruby-r - Use mruby for returning data to R

Generating datasets can be rather inconvenient and doing it directly in Ruby can be simpler for some.

Requirements

• compile tools (clang or tool that mruby requires to build)
• R (not needed at compile-time)

Installation

TL;DR

Run

rake

in a terminal. This should build everything you need and this also runs some examples (located in examples).

Longer explanation

mruby-r makes use of mruby. The Rakefile provided with mruby-r will:

• Clone
• Configure
• Build

mruby for you. The configuration file used by this process lives in the config/build_config.rb file. Feel free to edit it to include other gems or change some of the compile parameters

Running rake should produce the mruby-r shared library into the build directory.

Here are the current Rake tasks available (rake -T):

rake build_bridge  # Build a mruby/r bridge
rake clean         # Clean vendor
rake test          # Run test
rake vendor_mruby  # Build mruby in a vendor directory

Usage

mruby-r will make use of the static mruby library previously built. A bridge file will be created by the build system in order to produce a shared library, before being given to R's dyn.load function.

Given this R source file:

# script.r
# This script will generate 100 strings
dyn.load("/path/to/build/mruby-r")
values <- .C("mruby_r_eval", source="/any/source.rb", output=rep(c(''),each=1000))

dist <- values[2]

table(dist)
plot(table(dist))

and this Ruby script:

class DataSource
  def initialize
    @count = 0
    @elements = (0..100).map { |i| sprintf("e%03d", i) }
  end

  def next
    if @count < 1_000
      @count += 1
      @elements.sample.to_s
    else
      nil
    end
  end
end

DataSource # Don't forget to return the class at the end of the script

Executing R --slave --no-restore-data -f script.r should output:

dist
e000 e001 e002 e003 e004 e005 e006 e007 e008 e009 e010 e011 e012 e013 e014 e015
  11   14   12    9    9   13    7   10   12   11    9   10   13   13    9   10
e016 e017 e018 e019 e020 e021 e022 e023 e024 e025 e026 e027 e028 e029 e030 e031
   9   11    8   10   11    6   15   11    6    6   10   13   12    5    9   12
e032 e033 e034 e035 e036 e037 e038 e039 e040 e041 e042 e043 e044 e045 e046 e047
   8   13    9   12    9   13    6   11   18    7    8   10    8   10    8    7
e048 e049 e050 e051 e052 e053 e054 e055 e056 e057 e058 e059 e060 e061 e062 e063
   8    4   13   10   13    6   13    7   11    9   11   15    8   11   16   11
e064 e065 e066 e067 e068 e069 e070 e071 e072 e073 e074 e075 e076 e077 e078 e079
  13    8   10    9   10   12   14    9    4    7    7    7   10    6   12   16
e080 e081 e082 e083 e084 e085 e086 e087 e088 e089 e090 e091 e092 e093 e094 e095
  14    7   16    6   11   10   12   16    7   10   10    3    8   10    8   16
e096 e097 e098 e099 e100
   5    5    8   12    3

And a plot should have been generated:

Known limitations / Design choices

Scripts can return any type of objects but mruby-r will only return strings of type MRB_TT_STRING. Other types will be converted to strings in Ruby-land. This means developers will be given the opportunity to override to_s on those objects to fine-tune their representation before being casted in R.

License

Copyright (c) 2015 Franck Verrot. MIT LICENSE. See LICENSE.md for details.