Styling Leaflet circleMarkers by numerical properties and plotting them with Highcharts

Synthetic GeoJSON data are created with a quasi-normal spatial distribution and displayed as circle markers on a Leaflet map. The markers are styled using a color ramp that is tied to one numerical property ("year" in this case) and a size scale that is tied to another ("size"). The scatterplot of size vs. year is created using Highcharts and placed in a Leaflet control box.

by Alex Azuero

HTML

<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet-0.7.2/leaflet.css">
<script src="http://cdn.leafletjs.com/leaflet-0.7.2/leaflet.js"></script>
<script src="http://code.highcharts.com/highcharts.js"></script>
<script src="http://code.highcharts.com/modules/exporting.js"></script>
<div id="map"></div>

CSS

html, body, #map {
    height: 100%;
    width:100%;
    padding:0px;
    margin:0px;
    background: white;
}
.info {
    padding: 6px 8px;
    font: 14px/16px Arial, Helvetica, sans-serif;
    background: white;
    background: rgba(255, 255, 255, 0.8);
    box-shadow: 0 0 15px rgba(0, 0, 0, 0.2);
    border-radius: 5px;
}
.info h4 {
    margin: 0 0 5px;
    color: #777;
}
.legend {
    text-align: left;
    line-height: 18px;
    color: #555;
}
.legend i {
    width: 18px;
    height: 18px;
    float: left;
    margin-right: 8px;
    opacity: 0.7;
}
.legend .colorcircle {
    border-radius: 50%;
    width: 15px;
    height: 15px;
    margin-top: 0px;
}
.legend .circlepadding {
    border-radius: 50%;
    margin-top: 0px;
    background: rgba(255, 255, 255, 0.8);
}

JavaScript

/////////////////////////////////////////////////////////////////////////////////////////////
//setting up the map//
/////////////////////////////////////////////////////////////////////////////////////////////

// set center coordinates
var centerlat = 34.05;
var centerlon = -118.25;

// set default zoom level
var zoomLevel = 10;

// initialize map
var map = L.map('map').setView([centerlat, centerlon], zoomLevel);

// set source for map tiles
ATTR = '&copy; <a href="http://openstreetmap.org">OpenStreetMap</a> contributors, ' +
'<a href="http://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a> | ' +
'&copy; <a href="http://cartodb.com/attributions">CartoDB</a>';

CDB_URL = 'http://{s}.basemaps.cartocdn.com/light_all/{z}/{x}/{y}.png';

// add tiles to map
L.tileLayer(CDB_URL, {attribution: ATTR}).addTo(map);

/////////////////////////////////////////////////////////////////////////////////////////////
//creating some synthetic GeoJSON data//
/////////////////////////////////////////////////////////////////////////////////////////////

//initialize
var dotlayer;
var dots;
var dotcount = 800;

//cheapo normrand function
function normish(mean, range) {
    var num_out = ((Math.random() + Math.random() + Math.random() + Math.random() - 2) / 2) * range + mean;
    return num_out;
}

//create geojson data with random ~normal distribution
function make_dots() {

    dots = {
        type: "FeatureCollection",
        features: []
    };

    for (var i = 0; i < dotcount; ++i) {

        //set up random variables
        x = normish(0, 3);
        y = normish(0, 3);

        //create points randomly distributed about center coordinates
        var g = {
            "type": "Point",
                "coordinates": [((x * 0.1) + centerlon), ((y * 0.1) + centerlat)]
        };

        //create feature properties, roughly proportional to distance from center coordinates
        var p = {
            "id": i,
                "popup": "Dot_" + i,
                "year":...