functions: exponential moving average

dist/test/datasource-zabbix/dataProcessor.js

@@ -34,6 +34,9 @@ var scale = function scale(factor, datapoints) {
 var simpleMovingAverage = function simpleMovingAverage(n, datapoints) {
   return _timeseries2.default.simpleMovingAverage(datapoints, n);
 };
+var expMovingAverage = function expMovingAverage(a, datapoints) {
+  return _timeseries2.default.expMovingAverage(datapoints, a);
+};
 
 var SUM = _timeseries2.default.SUM;
 var COUNT = _timeseries2.default.COUNT;
@@ -125,6 +128,7 @@ var metricFunctions = {
   delta: delta,
   rate: rate,
   simpleMovingAverage: simpleMovingAverage,
+  expMovingAverage: expMovingAverage,
   aggregateBy: aggregateByWrapper,
   average: _lodash2.default.partial(aggregateWrapper, AVERAGE),
   min: _lodash2.default.partial(aggregateWrapper, MIN),

dist/test/datasource-zabbix/metricFunctions.js

@@ -80,6 +80,13 @@ addFuncDef({
   defaultParams: [10]
 });
 
+addFuncDef({
+  name: 'expMovingAverage',
+  category: 'Transform',
+  params: [{ name: 'smoothing', type: 'float', options: [0.001, 0.01, 0.05, 0.1, 0.2, 0.3, 0.5, 0.7, 0.9] }],
+  defaultParams: [0.2]
+});
+
 // Aggregate
 
 addFuncDef({

dist/test/datasource-zabbix/timeseries.js

@@ -277,6 +277,22 @@ function simpleMovingAverage(datapoints, n) {
   return sma;
 }
 
+function expMovingAverage(datapoints, a) {
+  var ema = [datapoints[0]];
+  var ema_prev = datapoints[0][POINT_VALUE];
+  var ema_cur = void 0;
+  for (var i = 1; i < datapoints.length; i++) {
+    if (datapoints[i][POINT_VALUE] !== null) {
+      ema_cur = a * datapoints[i][POINT_VALUE] + (1 - a) * ema_prev;
+      ema_prev = ema_cur;
+      ema.push([ema_cur, datapoints[i][POINT_TIMESTAMP]]);
+    } else {
+      ema.push([null, datapoints[i][POINT_TIMESTAMP]]);
+    }
+  }
+  return ema;
+}
+
 function COUNT(values) {
   return values.length;
 }
@@ -411,6 +427,7 @@ var exportedFunctions = {
   delta: delta,
   rate: rate,
   simpleMovingAverage: simpleMovingAverage,
+  expMovingAverage: expMovingAverage,
   SUM: SUM,
   COUNT: COUNT,
   AVERAGE: AVERAGE,