listing-6.9.js

//
// This example imports a CSV file, filters out an entire column and exports a new CSV file.
//
// This example uses Data-Forge.
//

"use strict";

const dataForge = require('data-forge');
const inputFileName = "./data/surveys.csv";
const outputFileName = "./output/surveys-aggregated.csv";

function transformData (inputDataFrame) {
    return inputDataFrame
        .parseFloats("transects_length")
        .groupBy(inputRow => inputRow.reef_name)
        .select(group => {
            return {
                reef_name: group.first().reef_name,
                transects_length: group
                    .deflate(row => row.transects_length)
                    .sum(),
            };
        })
        .inflate();
}

dataForge.readFile(inputFileName)
    .parseCSV()
    .then(inputDataFrame => {
        const outputDataFrame = transformData(inputDataFrame);
        return outputDataFrame
            .asCSV()
            .writeFile(outputFileName);
    })
    .then(() => {
        console.log("Done!");
    })
    .catch(err => {
        console.error("Error!");
        console.error(err && err.stack || err);
    });