Nord

Nord is a proof of concept micro-library that can be used to execute R scripts from Node.

Installation

For use with node and npm:

$ npm install --save @marianoviola/nord

Usage

In order to execute R scripts through nord you need a working R installation.

Module

const { run } = require("@marianoviola/nord");

run("./examples/eleventy/scripts/topten.R", ["json"])
  .then(data => console.log(data))
  .catch(err => console.log(err))

API

run(scriptPath, scriptArgs)

Executes a R script.

Arguments

scriptPath (string): The R script path.

scriptArgs (...Array): An array of arguments to pass to the R script.

Returns

(Promise<string>): The R script output decoded as UTF-8 string.

Examples

Eleventy

Nord can be used to execute R scripts making their output available to a static site generator such as Eleventy. Eleventy, for example, allows to dynamically generate data at build time using JavaScript data files:

const { run } = require("@marianoviola/nord");

module.exports = async function () {
  try {
    const data = await run("./scripts/topten.R", ["json"]);
    return JSON.parse(data);
  } catch (err) {
    throw err;
  }
};

examples/eleventy/_data/topten.js.

In the example above it is assumed that the R script is able to output a JSON string using for example cat() and jsonlite.

Build Eleventy using GitHub Actions

To execute R scripts using nord and then build eleventy using GitHub Actions you can use a workflow like this:

name: Exec R scripts and build Eleventy
on:
  push:
    branches:
    - master
jobs:
  nord:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Setup and install R packages
        uses: r-lib/actions/setup-r@v1
      - run: Rscript -e 'install.packages("remotes", repos = c(CRAN = "https://cloud.r-project.org"))'
      - run: Rscript -e 'remotes::install_github("rstudio/renv")'
      - run: Rscript -e 'renv::restore()'
      - name: Setup and run Node
        uses: actions/setup-node@v1
        with:
          node-version: '12.x'
      - run: npm install
      - run: npm run build

examples/eleventy/.github/workflows/nord.yml.

The workflow example above setups R using GitHub Actions for the R language and installs R packages using renv before running Node scripts.

Express

Nord can be also used to exec R scripts at runtime using Express or any another Node web framework. It can be an alternative to Plumber in creating REST API using data coming from R scripts:

const express = require("express");
const { run } = require("@marianoviola/nord");

const app = express();
const port = 3000;

app.get("/", async (req, res) => {
  try {
    const data = await run("./scripts/topten/topten.R", ["json"]);
    console.log(data);
    res.json(data);
  } catch (err)  {
    res.send(err);
  }
});

app.listen(port, () =>
  console.log(`Example app listening at http://localhost:${port}`)
);

examples/express/index.js.

You can run the Express example pulling and running the nord Docker image from Docker Hub:

$ docker pull marianoviola/nord
$ docker run --name nord -p 3000:3000 -d marianoviola/nord

CLI

Nord can be used via CLI using nord-cli a simple wrapper around nord.js.

Usage

nord-cli script-path [script-arguments ...] > [output]

Example

$ npx @marianoviola/nord ./examples/eleventy/scripts/topten.R json > ./examples/eleventy/_data/topten.json