block by mbostock 8460692

New York Population Density

Full Screen

Using New York Census Tracts.

index.html

<!DOCTYPE html>
<meta charset="utf-8">
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>

var width = 960,
    height = 700;

var path = d3.geo.path()
    .projection(null);

var color = d3.scale.threshold()
    .domain([1, 10, 50, 100, 500, 1000, 2000, 5000])
    .range(["#fff7ec", "#fee8c8", "#fdd49e", "#fdbb84", "#fc8d59", "#ef6548", "#d7301f", "#b30000", "#7f0000"]);

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

d3.json("ny.json", function(error, ny) {
  if (error) throw error;

  // group tracts by color for faster rendering
  svg.append("g")
      .attr("class", "tract")
    .selectAll("path")
      .data(d3.nest()
        .key(function(d) { return color(d.properties.population / d.properties.area * 2.58999e6); }) // convert square meters to square miles
        .entries(ny.objects.tracts.geometries))
    .enter().append("path")
      .style("fill", function(d) { return d.key; })
      .attr("d", function(d) { return path(topojson.merge(ny, d.values)); });
});

d3.select(self.frameElement).style("height", height + "px");

</script>

Makefile

GENERATED_FILES = \
	ny.json

all: $(GENERATED_FILES)

.PHONY: clean all

clean:
	rm -rf -- $(GENERATED_FILES) build

build/tl_2012_%_tract.zip:
	mkdir build
	curl -o $@ 'http://www2.census.gov/geo/tiger/TIGER2012/TRACT/$(notdir $@)'

build/tracts-unfiltered.shp: build/tl_2012_36_tract.zip
	rm -rf -- $(basename $@)
	mkdir -p $(basename $@)
	unzip -d $(basename $@) $<
	for file in $(basename $@)/*; do chmod 644 $$file; mv $$file $(basename $@).$${file##*.}; done
	rmdir $(basename $@)
	touch $@

# strip water tracts
build/tracts.shp: build/tracts-unfiltered.shp
	rm -f -- $@
	ogr2ogr -f 'ESRI Shapefile' -where 'SUBSTR(GEOID,6,2) != "99"' $@ $<

ny.json: build/tracts.shp
	node_modules/.bin/topojson \
		-o $@ \
		-e ACS_12_5YR_B01003_with_ann.csv \
		--id-property=GEO.id2,GEOID \
		-p population=+HD01_VD01,area=+ALAND \
		--projection 'width = 960, height = 700, d3.geo.mercator() \
			.center([-75.819, 42.795]) \
			.scale(6.5 * width) \
			.translate([width / 2, height / 2])' \
		--simplify=.5 \
		-- $(filter %.shp,$^)

package.json

{
  "name": "anonymous",
  "version": "0.0.1",
  "private": true,
  "devDependencies": {
    "d3": "3",
    "topojson": "1"
  }
}