aggregate = (dataset, typeName, colName, year) => {
const cleanDataset = dataset.map(d => ({...d, neighborhood: d['Neighborhood'].toLowerCase()}))
const sums = d3.rollup(cleanDataset, v => d3.sum(v, d => d[colName]), d => d.neighborhood)
return [...sums.keys()]
.filter(k => k.length > 0)
.map(k => ({neighborhood: k, type: typeName, units: sums.get(k), year}));
}