functions: simple moving average

dist/datasource-zabbix/timeseries.js

@@ -209,6 +209,49 @@ System.register(['lodash', './utils'], function (_export, _context) {
     return newSeries;
   }
 
+  function simpleMovingAverage(datapoints, n) {
+    var sma = [];
+    var w_sum = void 0;
+    var w_avg = null;
+    var w_count = 0;
+
+    // Initial window
+    for (var j = n; j > 0; j--) {
+      if (datapoints[n - j][POINT_VALUE] !== null) {
+        w_avg += datapoints[n - j][POINT_VALUE];
+        w_count++;
+      }
+    }
+    if (w_count > 0) {
+      w_avg = w_avg / w_count;
+    } else {
+      w_avg = null;
+    }
+    sma.push([w_avg, datapoints[n - 1][POINT_TIMESTAMP]]);
+
+    for (var i = n; i < datapoints.length; i++) {
+      // Insert next value
+      if (datapoints[i][POINT_VALUE] !== null) {
+        w_sum = w_avg * w_count;
+        w_avg = (w_sum + datapoints[i][POINT_VALUE]) / (w_count + 1);
+        w_count++;
+      }
+      // Remove left side point
+      if (datapoints[i - n][POINT_VALUE] !== null) {
+        w_sum = w_avg * w_count;
+        if (w_count > 1) {
+          w_avg = (w_sum - datapoints[i - n][POINT_VALUE]) / (w_count - 1);
+          w_count--;
+        } else {
+          w_avg = null;
+          w_count = 0;
+        }
+      }
+      sma.push([w_avg, datapoints[i][POINT_TIMESTAMP]]);
+    }
+    return sma;
+  }
+
   function COUNT(values) {
     return values.length;
   }
@@ -351,6 +394,7 @@ System.register(['lodash', './utils'], function (_export, _context) {
         scale_perf: scale_perf,
         delta: delta,
         rate: rate,
+        simpleMovingAverage: simpleMovingAverage,
         SUM: SUM,
         COUNT: COUNT,
         AVERAGE: AVERAGE,