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Algorithms for processing hourly time series data, with an initial focus onair quality monitoring applications.

This package supports theair-monitor ecosystem, whichworks with air quality monitoring data archives hosted by the US ForestService.

Note: All time series data are assumed to be on a regular hourly axiswith no gaps. Missing values should be represented asnull.

🚨 Important: All timestamp inputs must beLuxonDateTime objects in the UTC timezone.All timestamp outputs are also returned asDateTime objects in UTC.

High-level analysis functions:

• dailyStats(datetime, x, timezone)Returns local-time daily statistics (min, max, mean, count) from hourly data.

• diurnalStats(datetime, x, timezone, dayCount)Returns local-time hourly averages from the most recentdayCount days.

• pm_nowcast(pm)Calculates EPA-style NowCast values from hourly PM2.5 or PM10 data.

• trimDate(datetime, x, timezone)Trims input to full local-time days (midnight to midnight).

Array utility functions:

• arrayCount(x) — Count of non-missing (!= null) values
• arraySum(x) — Sum of valid values
• arrayMin(x) — Minimum valid value
• arrayMean(x) — Mean of valid values
• arrayMax(x) — Maximum valid value

To install the latest stable release fromnpm:

npm install air-monitor-algorithms

To install the latest development version directly from GitHub:

npm install github:MazamaScience/air-monitor-algorithms

This ES module can be used in modern JavaScript projects, including Svelteand Vue apps. You must use LuxonDateTime objects in UTC as input timestamps.

import {  dailyStats,  pm_nowcast} from "air-monitor-algorithms";import { DateTime } from "luxon";// Generate fake hourly data for 3 daysconst datetime = [];const x = [];const start = DateTime.fromISO("2023-07-01T00:00:00Z"); // UTCfor (let i = 0; i < 72; i++) {  datetime.push(start.plus({ hours: i }));       // UTC Luxon DateTime  x.push(50 + Math.sin(i / 3) * 10);             // sinusoidal variation}// Calculate daily statistics in the 'America/Los_Angeles' timezoneconst daily = dailyStats(datetime, x, "America/Los_Angeles");console.log(daily.mean); // → [meanDay1, meanDay2, meanDay3]// Apply NowCast to the hourly dataconst nowcast = pm_nowcast(x);console.log(nowcast.slice(-5)); // → last 5 hourly NowCast values

• air-monitor
• air-monitor-plots

GPL-3.0-or-later© 2024–2025 Jonathan Callahan / USFS AirFire