point-grouper

group geojson points into containing polygons

example

var fs = require('fs');
var path = require('path');
var grouper = require('point-grouper');

var g = grouper();
g.on('region', function (region) {
    console.log('REGION ' + region.name);
    var outfile = path.join(__dirname, 'output', region.name + '.geojson');
    region.pipe(fs.createWriteStream(outfile));
});

process.argv.slice(2).forEach(function (file) {
    var ws = g.createWriteStream();
    fs.createReadStream(file).pipe(ws);
});

Then give point-grouper some files. Here we'll provide oakland city council district boundaries for the polygons and oakland street tree data for the points.

$ mkdir -p output
$ node group.js districts.json trees.geojson
REGION 7
REGION 6
REGION 1
REGION 3
REGION 5
REGION 4
REGION 2

The program will then split up the tree data out into each district file:

$ ls -sh output/
total 41M
9.6M 1.geojson  6.7M 3.geojson  4.6M 5.geojson  4.0M 7.geojson
6.0M 2.geojson  4.9M 4.geojson  4.6M 6.geojson

You can also use the point-grouper command that ships with this module to do the same thing without having to use the API directly:

$ point-grouper districts.json trees.geojson -o output/

usage

usage: point-grouper FILES {-o OUTDIR}

methods

var grouper = require('point-grouper')

var g = grouper(cb)

Create a new grouper.

Optionally provide a cb(err, region) listener for 'error' and 'region' events.

g.createWriteStream()

events

g.on('region', function (region) {})

When a region (any polygon) was read from one of the input files, this event fires with region, a readable stream of geojson data for all of the points contained in the region.

The region stream has these properties:

• region.index - the numeric index of the region
• region.name - the property Name if one was present
• region.feature - the feature data for the region polygon
• region.coordinates - an array of the points in the region shape

install

With npm, to get the library do:

npm install point-grouper

and to get the point-grouper command do:

npm install -g point-grouper

license

MIT