chicago gun traces

<!DOCTYPE html>
<meta charset="utf-8">

<style>

body {
  background-color: #E3FDFD;
}

.counties {
  stroke: #bfbfbf;
  stroke-width: .25;
  fill: #fff; 
}

.states {
  stroke: #000;
  stroke-width: .25;
  fill: none;
}

#popoverText { 
  position: absolute;     
  text-align: center;         
  padding: 2px;       
  font-family: Futura;    
  background: #fff; 
  border: 0px;    
  border-radius: 8px;     
  pointer-events: none;
  opacity: 0;     
}

</style>

var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height");

var colorScale =  d3.scaleThreshold()
    .domain([1,910,1107,1880,2716,15782])
    .range(["rgb(247,251,255)","rgb(222,235,247)","rgb(198,219,239)","rgb(158,202,225)","rgb(107,174,214)","rgb(66,146,198)", "rgb(8,48,107)"]);

queue()
    .defer(d3.csv, "guns-history.csv")
    .defer(d3.json, "us.json")
    .await(ready);

function ready(error, guns, us) {
  if (error) throw error;

console.log(topojson.feature(us, us.objects.counties).features);

gunsLookup = {};

guns.forEach(function(d) {
    d.count3 = +d.count3;
    gunsLookup[d.FIPS] = d.count3;
  })

locationLookup = {};

guns.forEach(function(d) {
    locationLookup[d.FIPS] = d.county;
  })

var counties = topojson.feature(us, us.objects.counties),
      states = topojson.feature(us, us.objects.states);

var path = d3.geoPath()
      .projection(d3.geoAlbersUsa()
      .fitSize([width, height], counties));

var defs = svg.append("defs");

//Filter for the outside glow
    var filter = defs.append("filter")
    .attr("id","glow");
filter.append("feGaussianBlur")
    .attr("stdDeviation","3.5")
    .attr("result","coloredBlur");
var feMerge = filter.append("feMerge");
feMerge.append("feMergeNode")
    .attr("in","coloredBlur");
feMerge.append("feMergeNode")
    .attr("in","SourceGraphic");

svg.selectAll(".counties")
      .data(counties.features)
    .enter().append("path")
      .attr("class", "counties")
      .attr("d", path)
      .style("fill", function(d) { return gunsLookup[d.id] > 0 ? "#efefef" : "#fff" })
      .on("mouseenter", function(d) {

d3.select(this)
        .style("stroke-width", 1.5)

d3.select("#popoverText")
        .transition()
        .style("opacity", 1)
        .style("left", (d3.event.pageX) + "px")
        .style("top", (d3.event.pageY) + "px")
        .text(locationLookup[d.id])

})
    .on("mouseleave", function(d) { 
      d3.select(this)
        .style("stroke-width", .25)

d3.select("#popoverText")
        .transition()
        .style("opacity", 0);

});

svg.selectAll(".states")
    .data(states.features)
    .enter().append("path")
    .attr("class", "states")
    .attr("d", path)

d3.selectAll(".states")
    .style("filter", "url(#glow)");

svg.selectAll(".bubbles")
    .data(counties.features)
    .enter().append("g")
    .attr("class","bubbles")
    .attr("transform",function(d) { return "translate(" + path.centroid(d) + ")"})
    .append("circle")
    .attr("r", function(d) { return Math.sqrt(gunsLookup[d.id])/Math.PI; })
    .style("fill", function(d) { return colorScale(gunsLookup[d.id]); })
    .style("fill-opacity", .25)
    .style("stroke", "#000")
    .style("pointer-events","none")

d3.selectAll(".bubbles")
    .style("filter", "url(#glow)");

}

</script>
</body>

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

https://d3js.org/topojson.v1.min.js

https://cdnjs.cloudflare.com/ajax/libs/queue-async/1.0.7/queue.min.js