Volume by hour

// When a market trades: the average volume of each UTC hour of the day, and how far price moves
// in it, over every bar on the chart. The hours are names on an axis of their own, so the graphs
// show in a Script graphs panel, which the legend's Graphs button opens. Best on 1h bars or less.
indicator('Volume by hour', { overlay: true, shortName: 'By hour' });

const chart = bars();
// A sum and a count per hour, for each graph's average.
const volume = state.map<number>(24);
const moves = state.map<number>(24);
const counts = state.map<number>(24);
const started = state.bar<boolean>(false);

const byVolume = graph('Average volume by UTC hour', { axis: 'category' });
const volumeBars = byVolume.bars('Volume (USD)');
const byMove = graph('Average move by UTC hour', { axis: 'category', format: 'percent', precision: 2 });
const moveBars = byMove.bars('High to low');

const hourName = (hour: number) => `${hour < 10 ? '0' : ''}${hour}:00`;

chart.onBar(() => {
  // Every hour on the axis from the start, in order, so a quiet hour still has its place.
  if (!started.value) {
    started.value = true;
    for (let hour = 0; hour < 24; hour += 1) {
      volumeBars.set(hourName(hour), na);
      moveBars.set(hourName(hour), na);
    }
  }
  const key = hourName(clock.parts(chart.time).hour);
  const count = (counts.get(key) ?? 0) + 1;
  counts.set(key, count);
  volume.set(key, (volume.get(key) ?? 0) + chart.volume * chart.close);
  moves.set(key, (moves.get(key) ?? 0) + (chart.high - chart.low) / chart.open);
  volumeBars.set(key, volume.get(key)! / count);
  moveBars.set(key, (moves.get(key)! / count) * 100);
});