functions: exponential moving average

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,