functions: simple moving average

src/datasource-zabbix/dataProcessor.js

@@ -9,6 +9,7 @@ let sumSeries = ts.sumSeries;
 let delta = ts.delta;
 let rate = ts.rate;
 let scale = (factor, datapoints) => ts.scale_perf(datapoints, factor);
+let simpleMovingAverage = (n, datapoints) => ts.simpleMovingAverage(datapoints, n);
 
 let SUM = ts.SUM;
 let COUNT = ts.COUNT;
@@ -102,6 +103,7 @@ let metricFunctions = {
   scale: scale,
   delta: delta,
   rate: rate,
+  simpleMovingAverage: simpleMovingAverage,
   aggregateBy: aggregateByWrapper,
   average: _.partial(aggregateWrapper, AVERAGE),
   min: _.partial(aggregateWrapper, MIN),

src/datasource-zabbix/metricFunctions.js

@@ -57,6 +57,15 @@ addFuncDef({
   defaultParams: [],
 });
 
+addFuncDef({
+  name: 'simpleMovingAverage',
+  category: 'Transform',
+  params: [
+    { name: 'factor', type: 'int', options: [6, 10, 60, 600] }
+  ],
+  defaultParams: [10],
+});
+
 // Aggregate
 
 addFuncDef({

src/datasource-zabbix/timeseries.js

@@ -226,6 +226,49 @@ function rate(datapoints) {
   return newSeries;
 }
 
+function simpleMovingAverage(datapoints, n) {
+  let sma = [];
+  let w_sum;
+  let w_avg = null;
+  let w_count = 0;
+
+  // Initial window
+  for (let 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 (let 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;
 }
@@ -359,6 +402,7 @@ const exportedFunctions = {
   scale_perf,
   delta,
   rate,
+  simpleMovingAverage,
   SUM,
   COUNT,
   AVERAGE,