census block heatmap

gistfile1.coffee

  $.getJSON '/data/mn-blks.json', (data) ->  
    values = _.uniq(_.map(data.features, (d) -> d.counts[prop]))
    color  = d3.scale.quantile()
       .domain(values)
       .range(d3.range(4))
    # Add and clasify block-level geography
    map.add po.geoJson()
      .features(data.features)
      .on 'load', (d) ->
        _.each(d.features, (f) -> 
          e = f.element
          col = color(f.data.counts[prop])
          e.setAttribute('class', "nh q5-#{col}")
        )