d3.csv(
  "data.csv", 
  function convertRow(row) {
    // columns are: Campaign,Click Date,clicked
    return {
      campaign: row.Campaign,
      date: row['Click Date'],
      clicked: parseInt(row.clicked, 10)
    };
  }, 
  function onData(err, data) {
    console.log('given rows', data)
    var totals = data.reduce(function (byDate, entry) {
      var dateParser = d3.timeParse("%d/%m/%Y");
      var parsedDate = dateParser(entry.date);
      var formattedDate = d3.isoFormat(parsedDate);
      var key = formattedDate;

      // make sure we have a record for this date
      if (!byDate[key]) {
        byDate[key] = { date: formattedDate }
      }

      // make sure we have a total for this campaign
      if (!byDate[key][entry.campaign]) {
        byDate[key][entry.campaign] = 0
      }

      // increment the total for this campaign
      byDate[key][entry.campaign] += entry.clicked

      return byDate
    }, {})
    console.log('totals, by date', totals)
  }
)