diff --git a/src/datasource-zabbix/dataProcessor.js b/src/datasource-zabbix/dataProcessor.js
index 5e6dba2..e6e0e6f 100644
--- a/src/datasource-zabbix/dataProcessor.js
+++ b/src/datasource-zabbix/dataProcessor.js
@@ -37,6 +37,33 @@ function limit(order, n, orderByFunc, timeseries) {
   }
 }
 
+function removeAboveValue(n, datapoints) {
+  return _.map(datapoints, point => {
+    return [
+      (point[0] > n) ? null : point[0],
+      point[1]
+    ];
+  });
+}
+
+function removeBelowValue(n, datapoints) {
+  return _.map(datapoints, point => {
+    return [
+      (point[0] < n) ? null : point[0],
+      point[1]
+    ];
+  });
+}
+
+function transformNull(n, datapoints) {
+  return _.map(datapoints, point => {
+    return [
+      (point[0] !== null) ? point[0] : n,
+      point[1]
+    ];
+  });
+}
+
 function sortSeries(direction, timeseries) {
   return _.orderBy(timeseries, [function (ts) {
     return ts.target.toLowerCase();
@@ -123,6 +150,7 @@ let metricFunctions = {
   rate: rate,
   movingAverage: simpleMovingAverage,
   exponentialMovingAverage: expMovingAverage,
+  transformNull: transformNull,
   aggregateBy: aggregateByWrapper,
   // Predefined aggs
   percentil: percentil,
@@ -133,6 +161,8 @@ let metricFunctions = {
   sum: _.partial(aggregateWrapper, SUM),
   count: _.partial(aggregateWrapper, COUNT),
   sumSeries: sumSeries,
+  removeAboveValue: removeAboveValue,
+  removeBelowValue: removeBelowValue,
   top: _.partial(limit, 'top'),
   bottom: _.partial(limit, 'bottom'),
   sortSeries: sortSeries,
diff --git a/src/datasource-zabbix/metricFunctions.js b/src/datasource-zabbix/metricFunctions.js
index f4da830..498b99f 100644
--- a/src/datasource-zabbix/metricFunctions.js
+++ b/src/datasource-zabbix/metricFunctions.js
@@ -85,6 +85,15 @@ addFuncDef({
   defaultParams: [0.2],
 });
 
+addFuncDef({
+  name: 'transformNull',
+  category: 'Transform',
+  params: [
+    {name: 'number', type: 'float'}
+  ],
+  defaultParams: [0],
+});
+
 // Aggregate
 
 addFuncDef({
@@ -170,6 +179,24 @@ addFuncDef({
 
 // Filter
 
+addFuncDef({
+  name: 'removeAboveValue',
+  category: 'Filter',
+  params: [
+    {name: 'number', type: 'float'},
+  ],
+  defaultParams: [0],
+});
+
+addFuncDef({
+  name: 'removeBelowValue',
+  category: 'Filter',
+  params: [
+    {name: 'number', type: 'float'},
+  ],
+  defaultParams: [0],
+});
+
 addFuncDef({
   name: 'top',
   category: 'Filter',