Merge pull request #25 from oyve/dev

Dev

README.md

@@ -1,20 +1,21 @@
 ![Node.js CI](https://github.com/oyve/barometer-trend/workflows/Node.js%20CI/badge.svg)
 # barometer-trend
-Calculate the tendency and trend of a barometer for a one to three hour period with barometric weather predictions.
+Calculate the tendency and trend of a barometer for a *one* to *three* hour period including barometric weather predictions.
 
 ## Features
-- Tendency and trend of the barometer for the *last hour* or *three hours* (`FALLNG|SLOWLY`)- 
+- Tendency and trend of the barometer for the *last hour* or *three hours* (`FALLING|SLOWLY`)
 - Prediction of weather and systems:
-  - By pressure tendency only (`Expect gale force weather'`)
-  - By pressure tendency, thresholds and wind direction (`Increasing rain, clearing within 12 hours.`)
+  - By pressure trend only (`Expect gale force weather'`)
+  - By pressure trend, thresholds and wind direction (`Increasing rain, clearing within 12 hours.`)
   - By seasonal pressure thresholds for winter and summer (`Cloudy and humid, thunderstorms`)
   - Front system tendency for the last three hours (`Falling before a lesser rise` | `Cold front passage` | `Strong and gusty, then veers`)
   - Force wind expectation in Beaufort scale based on the pressure tendency (`F8-9`)
 - Detects current pressure system `Low`, `Normal`, `High`
 
 Note
-- All calculations corrected to sea level pressure by optional `altitude` and `temperature`
-- 48 hour history
+- Picks the period with the highest severity (one hour or three hours)
+- All calculations corrected (internally) to sea level pressure by optional `altitude` and `temperature`
+- Up to 48 hour history
 
 ## Install & Use
 ```
@@ -28,7 +29,7 @@ barometer.addPressure(datetime1, 101500);
 barometer.addPressure(datetime2, 101505);
 barometer.addPressure(datetime3, 101512, 100, 20, 225); //100 = altitude, 20 = C degrees, 225 = wind direction 
 
-//barometer.addPressure(...) is more presice when pressure is corrected by altitude and temperature.
+//barometer.addPressure(...) is more precise when pressure is corrected by altitude and temperature.
 
 let forecast = barometer.getPredictions(); //returns JSON
 ```

package.json

@@ -1,6 +1,6 @@
 {
   "name": "barometer-trend",
-  "version": "2.2.0",
+  "version": "2.2.2",
   "description": "Calculate the tendency, trend and weather predictions of barometric pressure",
   "main": "index.js",
   "directories": {

test/utils.test.js

@@ -6,7 +6,8 @@ describe("Utils Tests", function () {
 
 		it("it should equal", function () {
 			//arrange
-			const expected = new Date().getHours() - 3;
+			const now = new Date();
+			const expected = now.getHours() < 3 ? now.getHours() + 24 - 3 : now.getHours() - 3; //avoid midnight 00 to 02 problem
 			//act
 			var actual = utils.minutesFromNow(-180).getHours();
 			//assert
@@ -102,4 +103,23 @@ describe("Utils Tests", function () {
 			assert.strictEqual(actual.value, expected);
 		});
 	});
+
+	describe("getPressureAverageByTime Test", function () {
+
+		it("it should average", function () {
+			//arrange
+			const expected = 101950;
+			const pressures = [
+				{ datetime: utils.minutesFromNow(-59), value: 101800 },
+				{ datetime: utils.minutesFromNow(-30), value: 101900 },
+				{ datetime: utils.minutesFromNow(-10), value: 102000 },
+				{ datetime: utils.minutesFromNow(-1), value: 102100 }
+			];
+			let subset = utils.getPressuresByPeriod(pressures, utils.minutesFromNow(-60), new Date());
+			//act
+			var actual = utils.getPressureAverage(subset);
+			//assert
+			assert.strictEqual(actual, expected);
+		});
+	});
 });

trend.js

@@ -1,9 +1,5 @@
 const utils = require('./utils');
 
-const TWENTY_MINUTES = 20;
-const ONE_HOUR = 60;
-const THREE_HOURS = 180;
-
 const TENDENCY = {
 	RISING: { key: 'RISING' },
 	FALLING: { key: 'FALLING' }
@@ -52,8 +48,8 @@ function calculate(pressures, from) {
 		return {
 			tendency: tendency.key,
 			trend: threshold.trend.key,
-			from: earlier.value,
-			to: later.value,
+			from: earlier,
+			to: later,
 			difference: difference,
 			ratio: Math.abs(ratio),
 			period: Math.abs(from),

utils.js

@@ -12,7 +12,7 @@ const KELVIN = 273.15;
  * @returns {Date} Date with given minute difference
  */
 function minutesFromNow(minutes) {
-	var now = new Date();
+	let now = new Date();
 	now.setMinutes(now.getMinutes() + minutes);
 	return new Date(now);
 }
@@ -63,6 +63,32 @@ function getPressureClosestTo(pressures, datetime) {
 	return (diffNext < diffPrevious) ? next : previous;
 }
 
+/**
+ * 
+ * @param {Array<Object>} pressures Array of pressures
+ * @param {Date} startTime Period start
+ * @param {Date} endTime Period end
+ * @returns Subset of pressures of the given period
+ */
+function getPressuresByPeriod(pressures, startTime, endTime)
+{
+	return pressures.filter((p) => p.datetime.getTime() >= startTime.getTime() && p.datetime.getTime() <= endTime.getTime());
+}
+
+/**
+ * 
+ * @param {Array<Object>} pressures Array of pressures
+ * @returns Average pressure value
+ */
+function getPressureAverage(pressures) {
+	let sum = 0;
+	pressures.forEach((p) => {
+		sum += p.value;
+	});
+
+	return sum / pressures.length;
+}
+
 function isSummer(isNorthernHemisphere = true) {
     let month = new Date().getMonth() + 1;
 	let summer = month >= 4 && month <= 9; //April to September
@@ -86,6 +112,8 @@ module.exports = {
 	adjustPressureToSeaLevel,
 	toKelvinFromCelcius,
 	getPressureClosestTo,
+	getPressuresByPeriod,
+	getPressureAverage,
 	MINUTES,
 	KELVIN
 }