D3 Examples - Vector Tiles & Zoom_HW10

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<!DOCTYPE html>
<meta charset="utf-8">
​
<div class="title">
  <h1>Weekly display of Earthquakes in the United States <br>Case of Puerto Rico</br></h1> 
</div>
<style>
​
h1 {
  font-size: 1.6rem;
  text-transform: capitalize;
  font-weight: bold;
  color: red;
  font-family: "Cambria", cursive;
  text-align: center;
}
​
body {
  margin: 0;
}
​
.title {
  margin: auto;
  background: gold;
  width: 80%;
}
.map {
  position: relative;
  overflow: hidden;
}
​
.layer {
  position: absolute;
  will-change: transform;
}
​
.tile {
  position: absolute;
  width: 256px;
  height: 256px;
}
​
.tile path {
  fill: none;
  stroke: #000;
  stroke-linejoin: round;
  stroke-linecap: round;
}
​
.tile .major_road {
  stroke: #776;
}
​
.tile .minor_road {
  stroke: #ccb;
}
​
.tile .highway {
  stroke: #f39;
  stroke-width: 1.5px;
}
​
.tile .rail {
  stroke: #7de;
}
​
.info {
  color: #000;
  position: absolute;
  top: 450px;
  left: 800px;
  font-size: 20px;
}
​
​
</style>
<body>
<script src="//d3js.org/d3.v4.min.js"></script>
<script src="//d3js.org/d3-tile.v0.0.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>
​
var pi = Math.PI,
    tau = 2 * pi;
​
var width = Math.max(960, window.innerWidth),
    height = Math.max(500, window.innerHeight);
​
// Initialize the projection to fit the world in a 1×1 square centered at the origin.
var projection = d3.geoMercator()
    .scale(1 / tau)
    .translate([0, 0]);
​
var path = d3.geoPath()
    .projection(projection);
  
var tile = d3.tile()
    .size([width, height]);
​
var zoom = d3.zoom()
    .scaleExtent([1 << 20, 1 << 23])
    .on("zoom", zoomed);
        
var map = d3.select("body").append("div")
    .attr("class", "map")
    .style("width", width + "px")
    .style("height", height + "px")
    .on("mousemove", mousemoved);
​
var layer = map.append("div")
    .attr("class", "layer");
  
var info = map.append("div")
    .attr("class", "info");
  
var vector = map.append("path") //layer definition
        .attr("class", "path");
  
var quakes = map.append("g")//quakes layer definition
        .attr("class", "quake");
  
var us = "https://umbcvis.github.io/classes/class-03/us.json"
        
var usgs = "https://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_week.geojson";
​
d3.queue()
    .defer(d3.json, us)
    .defer(d3.json, usgs)
    .await(ready);
​
function ready(error, us, usgs) {
​
if (error) throw error;
  
  json = us;
​
  vector
      .datum(topojson.mesh(us, us.objects.us)); // bind the data for the US states but not drawing it, just setting it up
  
  quakes = quakes.selectAll(".quake")
                .data(usgs.features)//bind the data; enter, update and exit
                .enter().append('path')
                .attr('class', 'quake')
                .style('fill', 'crimson')
       
// Compute the projected initial center.
var center = projection([-85, 35]);
​
// Apply a zoom transform equivalent to projection.{scale,translate,center}.
map .call(zoom)
    .call(zoom.transform, d3.zoomIdentity
        .translate(width / 2, height / 2)
        .scale(1 << 20)
        .translate(-center[0], -center[1]));
}
​
function zoomed() {
  var transform = d3.event.transform;
​
  var tiles = tile
      .scale(transform.k)
      .translate([transform.x, transform.y])
      ();
​
  projection
      .scale(transform.k / tau)
      .translate([transform.x, transform.y]);
  
    vector
      .attr("d", path);
  quakes
        .attr("d", path);
​
 var image = layer
    .style("transform", stringify(tiles.scale, tiles.translate))
    .selectAll(".tile")
    .data(tiles, function(d) { return d; });
​
  image.exit()
      .each(function(d) { this._xhr.abort(); })
      .remove();
​
  image.enter().append("svg")
      .attr("class", "tile")
      .style("left", function(d) { return d[0] * 256 + "px"; })
      .style("top", function(d) { return d[1] * 256 + "px"; })
      .each(function(d) { this._xhr = render(d, this); });
}
​
function render(d, node) {
  return d3.json("https://vector.mapzen.com/osm/roads/" + d[2] + "/" + d[0] + "/" + d[1] + ".json?api_key=vector-tiles-LM25tq4", function(error, json) {
    if (error) throw error;
    var k = Math.pow(2, d[2]) * 256; // size of the world in pixels
​
    d3.select(node).selectAll("path")
      .data(json.features.sort(function(a, b) { return a.properties.sort_key - b.properties.sort_key; }))
      .enter().append("path")
        .attr("class", function(d) { return d.properties.kind; })
        .attr("d", d3.geoPath()
            .projection(d3.geoMercator()
                .scale(k / tau)
                .translate([k / 2 - d[0] * 256, k / 2 - d[1] * 256])
                .precision(0)));
  });
}
​
function stringify(scale, translate) {
  var k = scale / 256, r = scale % 1 ? Number : Math.round;
  return "matrix3d(" + [k, 0, 0, 0, 0, k, 0, 0, 0, 0, k, 0, r(translate[0] * scale), r(translate[1] * scale), 0, 1 ] + ")";
}
​
function mousemoved() {
  info.text(formatLocation(projection.invert(d3.mouse(this)), d3.zoomTransform(this).k));
}
​
function formatLocation(p, k) {
  var format = d3.format("." + Math.floor(Math.log(k) / 2 - 2) + "f");
  return (p[1] < 0 ? format(-p[1]) + "°S" : format(p[1]) + "°N") + " "
       + (p[0] < 0 ? format(-p[0]) + "°W" : format(p[0]) + "°E");
}
​
</script>
    