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Class 2-Oklahoma Earthquake

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<!DOCTYPE html>
<meta charset="utf-8">
<title>class-02 demo</title>

<style>
.line {
  fill: none;
  stroke: black;
  stroke-width: 1px;
}
rect {
  fill: none;
  stroke: black;
  stroke-width: 1px;
}
path.quake, circle.quake {
  fill: crimson;
  fill-opacity: 0.4;
}
path.counties, path.county-border {
  fill: none;
  stroke: #000;
  stroke-opacity: .2;
}
path.state {
  fill: none;
  stroke: #000;
}
</style>

<script src="https://d3js.org/d3.v4.min.js"></script>
<script src="https://d3js.org/topojson.v2.min.js"></script>
<body>
<script>
var width = 960;
var height = 500;
var smallest = 2.5; // threshold magnitude
var data = null; // global variable
// Set the map projection centered on Oklahoma
var projection = d3.geoAlbersUsa()
    .scale(7543)
    .translate([702, -186]);
var path = d3.geoPath()
    .pointRadius(5)
    .projection(projection);
var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);
var layer1 = svg.append("g");
var layer2 = svg.append("g");
var base = "https://gist.githubusercontent.com/pbogden/935370a5272acff2618b/raw/f4d102d819066bb21a0021b4cbab6502e86bf587/";
var usgs = "https://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_week.geojson";
// Read and plot the earthquake data
var url = base + "quakes.json";
d3.json(url, plotQuakes);
//d3.json(usgs, plotQuakes);
// Read and plot the state & county boundaries  
d3.json(base + "ok.json", plotState);
function plotQuakes(error, json) {
  if (error) console.log(error);
  
  // Assign the json to a global so we can manipulate it in the console
  data = json;
  
  // Filter the small earthquakes
  var features = data.features.filter(function(d) { return (+ d.properties.mag >= smallest) });
  // Plot the earthquakes
  layer2.selectAll("path.quake")
      .data(features)
    .enter().append("path")
      .attr("class", "quake")
      .attr("d", path)
}
function plotState(error, ok) {
  if (error) console.log(error);
  
  var objects = ok.objects.ok;
  var all = topojson.merge(ok, objects.geometries);
  
  layer1.append("path")
      .datum(all)
      .attr("class", "state")
      .attr("d", path);
  
  layer1.append("path")
      .datum(topojson.mesh(ok, objects, function(a, b) { return a !== b; }))
      .attr("class", "county-border")
      .attr("d", path);
 }
</script>

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

https://d3js.org/topojson.v2.min.js