Mapping SVG points on a map with Leaflet + D3 (v4)

Note: this example is built with D3.V4. Source code for this project is here. Filtering the original data set was done with a python script.

<!DOCTYPE html>
<html>
<head>
	<title>Map of parking meters in San Francisco, built with d3.js with leaflet.js</title>

// ToDo: add legends to explain coloring of daata points
		
		var c1 = ['#ccebc5', '#a8ddb5', '#7bccc4', '#4eb3d3', '#2b8cbe', '#0868ac', '#084081']
		var c2 = ['#a6cee3', '#1f78b4', '#b2df8a', '#33a02c', '#fb9a99', '#fdbf6f', '#ff7f00', '#cab2d6', '#6a3d9a'];
		
		// these palettes from from https://colorbrewer2.org/
		// colors ranging from cool blue to hot red...
		var c3 = ['#4575b4','#91bfdb','#e0f3f8','#ffffbf','#fee090','#fc8d59','#d73027'];

// colors ranging from icy blue to purple
		var c4 = ['#edf8fb','#bfd3e6','#9ebcda','#8c96c6','#8c6bb1','#88419d','#6e016b'];

// ToDo: find better way to do this!!!!
		function colors(n) {
			var colors = c1;
			return colors[n % colors.length];
		}

var currentColoring = 0;
		var currentZoom = 13; //8; //12;

mapLink = 
            '<a href="https://openstreetmap.org">OpenStreetMap</a>';

//-----------------------------------------------------------
		// NOTE: You'll need to get your own access Token from Mapbox
		//       Dev account sign up is easy and free, with some dev Tokens included
		//		 https://www.mapbox.com/help/define-access-token/
		//-----------------------------------------------------------
       	var mbAttr = 'Map data &copy; <a href="https://openstreetmap.org">OpenStreetMap</a> contributors, ' +
				'<a href="https://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a>, ' +
				'Imagery © <a href="https://mapbox.com">Mapbox</a>',
			mbUrl = 'https://api.tiles.mapbox.com/v4/{id}/{z}/{x}/{y}.png?access_token=pk.eyJ1Ijoia3Jpc3RpbmhlbnJ5IiwiYSI6ImNqMWdxMjd5aDAwM28zM2xtaGV2azYwcjYifQ.NTJiOqcnhP-_3etf4aZYmQ';

var grayscale   = L.tileLayer(mbUrl, {id: 'mapbox.light', attribution: mbAttr}),
		    streets  = L.tileLayer(mbUrl, {id: 'mapbox.streets',   attribution: mbAttr});

var map = L.map('map', {layers: [grayscale]}).setView([37.77139, -122.44486], currentZoom);

var baseLayers = {
			"Grayscale": grayscale,
			"Streets": streets
		};

L.control.layers(baseLayers).addTo(map);

// Add custom control for switching between dot colorings
		// 					https://www.coffeegnome.net/control-button-leaflet/
		// 					https://gis.stackexchange.com/questions/60576/custom-leaflet-controls
		var myControl = L.Control.extend({

options: {
		    position: 'topright' 
		    //control position - allowed: 'topleft', 'topright', 'bottomleft', 'bottomright'
		  },

onAdd: function (map) {
		    var container = L.DomUtil.create('div', 'leaflet-bar leaflet-control leaflet-control-custom');

L.DomEvent
		    .addListener(container, 'click', L.DomEvent.stopPropagation)
            .addListener(container, 'click', L.DomEvent.preventDefault)

container.style.backgroundColor = 'white';
		    container.style.width = '30px';
		    container.style.height = '30px';
		    container.status = 0;  // my own variable

container.onclick = function(){
		    	console.log(container.status);

// might want to do this as a switch statement, if many more cases
		    	if(container.status == 0){
		      		container.status = 1;
		      	} else if(container.status == 1){
		      		container.status = 0;
		      	}

changeColoring(container.status);
		    }
		    return container;
		  }

});

map.addControl(new myControl());

function changeColoring(status){
		currentColoring = status;
		update();
	}
				
	/* Initialize the SVG layer */
	map._initPathRoot()

/* We simply pick up the SVG from the map object */
	var svg = d3.select("#map").select("svg"),
	g = svg.append("g");
	var	d3_features;
	var transform;
	var path;
	var feature;
	var ids;
	var caps;

function strToLocation(s){
		var arr = s.slice(1,-1).split(',');
		arr[0] = parseFloat(arr[0]);
		arr[1] = parseFloat(arr[1]);
		return arr;
	}

capColors = {
		"Grey": '#999',
		"Green": '#FF0',
		"Yellow": 'yellow',
		"Black": 'black',
		"Red": 'red',
		"Brown": 'brown',
		"Purple": 'purple',
		"Undefined": '#ccc'

}

function getCapColor(d){
		return capColors[d['CAP_COLOR']];
	}

// Load data and plot it on map
	var datafile = "Parking_meters_sm.csv"; 
	d3.csv(datafile, function(data){

ids = d3.map(data, function(d){return d['RATEAREA'];}).keys()
		console.log(ids);

caps = d3.map(data, function(d){return d['CAP_COLOR']}).keys();
		console.log(caps)

data.forEach(function(d) {

d.loc = strToLocation(d['LOCATION']);
			
			try{
				d.LatLng = new L.LatLng(d.loc[0], d.loc[1]);
			} catch(err) {
				console.log('error', d.LatLng, err)
			}

d.color = getColor(d, ids);

var i = ids.indexOf(d['RATEAREA'])
			
		})

feature = g.selectAll("circle")
			.data(data)
			.enter().append("circle")
			.style("stroke", function(d){ return d.color; })  
			.style("opacity", .6) 
			.style("fill", function(d){return getFill(d) })
			.attr("r", function(d){return getR(d)});

// create a d3.geoPath to convert GeoJSON to SVG
		transform = d3.geoTransform({point: projectPoint});
	 	path = d3.geoPath().projection(transform);

map.on("viewreset", update);
		update();

})

function update() {
			currentZoom = map.getZoom();
			
			// reposotion dots
			feature.attr("transform", 
				function(d) { 
					return "translate("+ 
						map.latLngToLayerPoint(d.LatLng).x +","+ 
						map.latLngToLayerPoint(d.LatLng).y +")";
				})

if(currentColoring == 1){
				feature.style('fill', function(d){ return getCapColor(d); })
				feature.style('stroke', function(d){  return getCapColor(d); })
			} else {
				feature.style('fill', function(d){ return getColor(d, ids); })
				feature.style('stroke', function(d){  return getColor(d, ids); })
			}

// ToDo: show fewer dots when zoomed out
			// // update syle of dots, according to zoom level
			// if(currentZoom < 12){
			// 			feature.style('opacity', function(d){ if(d['CAP_COLOR'] > 5){return 1;}
			// 													else{ return .3}} )	
			// 			feature.attr('r', function(d){ if(d['CAP_COLOR'] > 5){return 2;}
			// 													else{ return 1}} )	
			// } else {
			// 	feature.style('opacity', .6);
			// }
			
		}

// Use Leaflet to implement a D3 geometric transformation.
		function projectPoint(x, y) {
			var point = map.latLngToLayerPoint(new L.LatLng(y, x));
			this.stream.point(point.x, point.y);
		}

//---------------------------------
	// for popup, when map is clicked
	var popup = L.popup();

function onMapClick(e) {
    	popup
        .setLatLng(e.latlng)
        .setContent("You clicked the map at " + e.latlng.toString())
        .openOn(map);
	}

map.on('click', onMapClick);
	//---------------------------------

function createJSON(data, d_id){
		var shapeJSON = {'features': [{
			'type': 'Feature',
			'geometry': {
				'type':'Polygon',
				'coordinates': data
			},
			'District': d_id
		}]}

return shapeJSON;
	}

function getR(d){
		
		return 1; 
	}

function getFill(d){
		return d.color;
	}

function getColor(d, ids){ 
			return colors(ids.indexOf(d['RATEAREA']))
	}

</script>
</body>
</html>

Modified http://d3js.org/d3.v4.min.js to a secure url

Modified http://cdn.leafletjs.com/leaflet-0.7/leaflet.js to a secure url

https://d3js.org/d3.v4.min.js

https://cdn.leafletjs.com/leaflet-0.7/leaflet.js