Using time_of(), library(), function()

This script paints Volume histogram with an "average volume for given time" line atop of it. This average volume is average volume for a given time of a day (i.e, 09:30) at a given time frame. In case if the current candle's volume is above the "typical volume for that time of a day" then its histogram column will be dark. Otherwise, it will be pale.

Example of reading it: avg volume for 09:30 at SPY,10 is 2.45M. Today it's 2.0M which is below the average, so the volume column will be pale.

describe_indicator('Volume by time', 'lower');

if (isNaN(constants.resolution)) {
    throw Error('This indicator can only work on intraday charts');
}

const tinycolor = library('tinycolor2');

const volumeByTime = {};
const lookbackPeriod = input('Lookback', 5, { min: 1, max: 10 });

function computeAverageVolume(candleVolume, candleTime) {
    const timeOfDay = time_of(candleTime);
    const timeHash = `${timeOfDay.hours}:${timeOfDay.minutes}`;

    if (!volumeByTime[timeHash]) {
        volumeByTime[timeHash] = [];
    }

    const avgVolume = volumeByTime[timeHash].
        slice(-lookbackPeriod).
        reduce((result, value) => result + value, 0) / lookbackPeriod;

    volumeByTime[timeHash].push(candleVolume);

    return volumeByTime[timeHash].length >= lookbackPeriod + 1
        ? avgVolume
        : null;
}

const averageVolumes = for_every(volume, time, computeAverageVolume);

const volumeColors = for_every(close, open, averageVolumes, volume, (c, o, avg, vol) => {
    if (vol > avg) {
        return c > o ? '#009900' : '#ee0000';
    }

    return c > o ? '#cddfcc' : '#ffe7e7';
});

paint(averageVolumes, { style: 'line', color: 'blue' });
paint(volume, { style: 'histogram', color: volumeColors });