data_rollup.coffee

  process = (data) ->
    keyMaker = (d) ->
      time = d.time
      if time not instanceof Date
        time = new Date(time * 1000)
      +d3.time.day.floor(time) / 1000

    nestedData = d3.nest()
      .key(keyMaker)
      .rollup((v) -> d3.sum(v, (d) -> d.value))
      .sortKeys(d3.ascending)
      .entries(data)

    nestedData.map (d) -> time: new Date(d.key * 1000), value: d.values