avg_cases_per_day = unique_states.map(state_name => {
let obj = { state: state_name };
let this_state_data = state_data.filter(d => d.state == state_name);
const data = this_state_data.map((d, i) => {
let new_cases = 0;
if (i === 0) new_cases = +d.cases;
else new_cases = +d.cases - +this_state_data[i - 1].cases;
return { date: d.date, new_cases: new_cases };
});
obj.avg_cases_per_day = d3.sum(data, d => d.new_cases) / data.length;
return obj;
})