diff --git a/numass-core/src/main/java/inr/numass/data/NumassDataUtils.java b/numass-core/src/main/java/inr/numass/data/NumassDataUtils.java
index ef8ef6c1..6a4a33b7 100644
--- a/numass-core/src/main/java/inr/numass/data/NumassDataUtils.java
+++ b/numass-core/src/main/java/inr/numass/data/NumassDataUtils.java
@@ -120,7 +120,7 @@ public class NumassDataUtils {
 //        Arrays.setAll(array, i -> Math.max(0, point.getSpectrum()[i] - reference.getSpectrum()[i]));
 //        return new NumassPointImpl(
 //                point.getVoltage(),
-//                point.getStartTime(),
+//                point.getTime(),
 //                point.getLength(),
 //                array
 //        );
diff --git a/numass-core/src/main/java/inr/numass/data/analyzers/AbstractAnalyzer.java b/numass-core/src/main/java/inr/numass/data/analyzers/AbstractAnalyzer.java
index bdb31b06..25d4cded 100644
--- a/numass-core/src/main/java/inr/numass/data/analyzers/AbstractAnalyzer.java
+++ b/numass-core/src/main/java/inr/numass/data/analyzers/AbstractAnalyzer.java
@@ -31,12 +31,14 @@ public abstract class AbstractAnalyzer implements NumassAnalyzer {
     }
 
     /**
-     * Return unsorted stream of events including events from frames
+     * Return unsorted stream of events including events from frames.
+     * In theory, events after processing could be unsorted due to mixture of frames and events.
+     * In practice usually block have either frame or events, but not both.
      *
      * @param block
      * @return
      */
-    public Stream<NumassEvent> getEventStream(NumassBlock block, Meta config) {
+    public Stream<NumassEvent> getEvents(NumassBlock block, Meta config) {
         if (block.getFrames().count() == 0) {
             return block.getEvents();
         } else if (getProcessor() == null) {
diff --git a/numass-core/src/main/java/inr/numass/data/analyzers/SimpleAnalyzer.java b/numass-core/src/main/java/inr/numass/data/analyzers/SimpleAnalyzer.java
index 3740baf9..9c30e448 100644
--- a/numass-core/src/main/java/inr/numass/data/analyzers/SimpleAnalyzer.java
+++ b/numass-core/src/main/java/inr/numass/data/analyzers/SimpleAnalyzer.java
@@ -25,7 +25,7 @@ public class SimpleAnalyzer extends AbstractAnalyzer {
     }
 
     public Stream<NumassEvent> getEventStream(NumassBlock block, int loChannel, int upChannel) {
-        return getEventStream(block, Meta.empty()).filter(it -> it.getChanel() >= loChannel && it.getChanel() < upChannel);
+        return getEvents(block, Meta.empty()).filter(it -> it.getChanel() >= loChannel && it.getChanel() < upChannel);
     }
 
     @Override
diff --git a/numass-core/src/main/java/inr/numass/data/analyzers/TimeAnalyzer.java b/numass-core/src/main/java/inr/numass/data/analyzers/TimeAnalyzer.java
index e8f6102c..96d70af2 100644
--- a/numass-core/src/main/java/inr/numass/data/analyzers/TimeAnalyzer.java
+++ b/numass-core/src/main/java/inr/numass/data/analyzers/TimeAnalyzer.java
@@ -31,12 +31,12 @@ public class TimeAnalyzer extends AbstractAnalyzer {
     public Values analyze(NumassBlock block, Meta config) {
         int loChannel = config.getInt("window.lo", 0);
         int upChannel = config.getInt("window.up", Integer.MAX_VALUE);
-        long t0 = config.getValue("t0").longValue();
+        long t0 = getT0(block, config);
 
         AtomicLong totalN = new AtomicLong(0);
         AtomicLong totalT = new AtomicLong(0);
 
-        extendedEventStream(block, config)
+        getEventsWithDelay(block, config)
                 .filter(pair -> {
                     short channel = pair.getKey().getChanel();
                     return channel >= loChannel && channel < upChannel;
@@ -73,6 +73,10 @@ public class TimeAnalyzer extends AbstractAnalyzer {
         }
     }
 
+    private long getT0(NumassBlock block, Meta config) {
+        return config.getValue("t0",0).longValue();
+    }
+
     /**
      * The chain of event times in nanos
      *
@@ -80,32 +84,41 @@ public class TimeAnalyzer extends AbstractAnalyzer {
      * @param config
      * @return
      */
-    public Stream<Pair<NumassEvent, Long>> extendedEventStream(NumassBlock block, Meta config) {
-        long t0 = config.getValue("t0").longValue();
+    public Stream<Pair<NumassEvent, Long>> getEventsWithDelay(NumassBlock block, Meta config) {
+        long t0 = getT0(block, config);
 
         AtomicReference<NumassEvent> lastEvent = new AtomicReference<>(null);
 
-        return super.getEventStream(block, config) //using super implementation
-                .sorted()
-                .map(event -> {
-                    if (lastEvent.get() == null) {
-                        lastEvent.set(event);
-                        return new Pair<>(event, 0L);
-                    } else {
-                        long res = event.getTimeOffset() - lastEvent.get().getTimeOffset();
-                        if (res >= 0) {
-                            lastEvent.set(event);
-                            return new Pair<>(event, res);
-                        } else {
-                            lastEvent.set(null);
-                            return new Pair<>(event, 0L);
-                        }
-                    }
-                }).filter(pair -> pair.getValue() >= t0);
+        Stream<NumassEvent> eventStream = super.getEvents(block, config);//using super implementation
+        if (config.getBoolean("sort", false)) {
+            eventStream = eventStream.sorted();
+        }
+
+        return eventStream.map(event -> {
+            if (lastEvent.get() == null) {
+                lastEvent.set(event);
+                return new Pair<>(event, 0L);
+            } else {
+                long res = event.getTimeOffset() - lastEvent.get().getTimeOffset();
+                if (res >= 0) {
+                    lastEvent.set(event);
+                    return new Pair<>(event, res);
+                } else {
+                    lastEvent.set(null);
+                    return new Pair<>(event, 0L);
+                }
+            }
+        }).filter(pair -> pair.getValue() >= t0);
     }
 
+    /**
+     * The filtered stream of events
+     * @param block
+     * @param config
+     * @return
+     */
     @Override
-    public Stream<NumassEvent> getEventStream(NumassBlock block, Meta config) {
-        return extendedEventStream(block,config).map(Pair::getKey);
+    public Stream<NumassEvent> getEvents(NumassBlock block, Meta config) {
+        return getEventsWithDelay(block, config).map(Pair::getKey);
     }
 }
diff --git a/numass-core/src/main/java/inr/numass/data/api/MetaBlock.java b/numass-core/src/main/java/inr/numass/data/api/MetaBlock.java
index f6bf1be6..33a785cb 100644
--- a/numass-core/src/main/java/inr/numass/data/api/MetaBlock.java
+++ b/numass-core/src/main/java/inr/numass/data/api/MetaBlock.java
@@ -32,11 +32,11 @@ public class MetaBlock implements NumassBlock {
 
     @Override
     public Stream<NumassEvent> getEvents() {
-        return blocks.stream().flatMap(NumassBlock::getEvents);
+        return blocks.stream().flatMap(NumassBlock::getEvents).sorted(Comparator.comparing(NumassEvent::getTime));
     }
 
     @Override
     public Stream<NumassFrame> getFrames() {
-        return blocks.stream().flatMap(NumassBlock::getFrames);
+        return blocks.stream().flatMap(NumassBlock::getFrames).sorted(Comparator.comparing(NumassFrame::getTime));
     }
 }
diff --git a/numass-core/src/main/java/inr/numass/data/api/NumassAnalyzer.java b/numass-core/src/main/java/inr/numass/data/api/NumassAnalyzer.java
index 0ac32f42..985d05e3 100644
--- a/numass-core/src/main/java/inr/numass/data/api/NumassAnalyzer.java
+++ b/numass-core/src/main/java/inr/numass/data/api/NumassAnalyzer.java
@@ -74,7 +74,7 @@ public interface NumassAnalyzer {
     String COUNT_KEY = "count";
     String LENGTH_KEY = "length";
     String COUNT_RATE_KEY = "cr";
-    String COUNT_RATE_ERROR_KEY = "cr.err";
+    String COUNT_RATE_ERROR_KEY = "crErr";
 
     /**
      * Perform analysis on block. The values for count rate, its error and point length in nanos must
@@ -91,7 +91,7 @@ public interface NumassAnalyzer {
      * @param block
      * @return
      */
-    Stream<NumassEvent> getEventStream(NumassBlock block, Meta config);
+    Stream<NumassEvent> getEvents(NumassBlock block, Meta config);
 
     /**
      * Analyze the whole set. And return results as a table
@@ -121,7 +121,7 @@ public interface NumassAnalyzer {
         //optimized for fastest computation
         //TODO requires additional performance optimization
         AtomicLong[] spectrum = new AtomicLong[MAX_CHANNEL];
-        getEventStream(block, config).forEach(event -> {
+        getEvents(block, config).forEach(event -> {
             if (spectrum[event.getChanel()] == null) {
                 spectrum[event.getChanel()] = new AtomicLong(1);
             } else {
diff --git a/numass-core/src/main/java/inr/numass/data/api/NumassFrame.java b/numass-core/src/main/java/inr/numass/data/api/NumassFrame.java
index 3e77246c..0d7c61a8 100644
--- a/numass-core/src/main/java/inr/numass/data/api/NumassFrame.java
+++ b/numass-core/src/main/java/inr/numass/data/api/NumassFrame.java
@@ -32,7 +32,7 @@ public class NumassFrame {
         this.tickSize = tickSize;
     }
 
-    public Instant getStartTime() {
+    public Instant getTime() {
         return startTime;
     }
 
diff --git a/numass-core/src/main/java/inr/numass/data/storage/NumassDataLoader.java b/numass-core/src/main/java/inr/numass/data/storage/NumassDataLoader.java
index 400a078c..4b848d4d 100644
--- a/numass-core/src/main/java/inr/numass/data/storage/NumassDataLoader.java
+++ b/numass-core/src/main/java/inr/numass/data/storage/NumassDataLoader.java
@@ -110,7 +110,6 @@ public class NumassDataLoader extends AbstractLoader implements ObjectLoader<Env
         }
     }
 
-
     /**
      * The name of informational meta file in numass data directory
      */
@@ -222,7 +221,7 @@ public class NumassDataLoader extends AbstractLoader implements ObjectLoader<Env
 
     @Override
     public Instant getStartTime() {
-        if (meta.hasValue("start_time")) {
+        if (meta().hasValue("start_time")) {
             return meta().getValue("start_time").timeValue();
         } else {
             return NumassSet.super.getStartTime();
diff --git a/numass-main/build.gradle b/numass-main/build.gradle
index 7d61967e..137f7c41 100644
--- a/numass-main/build.gradle
+++ b/numass-main/build.gradle
@@ -16,6 +16,10 @@ dependencies {
     compile "hep.dataforge:grind-terminal" //project(':dataforge-grind:grind-terminal')
 }
 
+idea{
+
+}
+
 //task listActions(dependsOn: classes, type: JavaExec) {
 //    main "inr.numass.LaunchGrindShell"
 //    args "-lc"
diff --git a/numass-main/src/main/groovy/inr/numass/data/PointAnalyzer.groovy b/numass-main/src/main/groovy/inr/numass/data/PointAnalyzer.groovy
index 54df3e6f..c5d4e89f 100644
--- a/numass-main/src/main/groovy/inr/numass/data/PointAnalyzer.groovy
+++ b/numass-main/src/main/groovy/inr/numass/data/PointAnalyzer.groovy
@@ -8,7 +8,7 @@ import hep.dataforge.values.Values
 import inr.numass.data.analyzers.TimeAnalyzer
 import inr.numass.data.api.NumassBlock
 
-import java.util.stream.DoubleStream
+import java.util.stream.LongStream
 
 /**
  * Created by darksnake on 27-Jun-17.
@@ -20,23 +20,28 @@ class PointAnalyzer {
 
     static Histogram histogram(NumassBlock point, int loChannel = 0, int upChannel = 10000, double binSize = 0.5, int binNum = 500) {
         return UnivariateHistogram.buildUniform(0d, binSize * binNum, binSize)
-                .fill(analyzer.extendedEventStream(point, Grind.buildMeta("window.lo": loChannel, "window.up": upChannel)).mapToDouble {it.value / 1000 as double})
+                .fill(analyzer.getEventsWithDelay(point, Grind.buildMeta("window.lo": loChannel, "window.up": upChannel))
+                .mapToDouble {
+                    it.value / 1000 as double
+                })
     }
 
-    static Histogram histogram(DoubleStream stream, double binSize = 0.5, int binNum = 500) {
-        return UnivariateHistogram.buildUniform(0d, binSize * binNum, binSize).fill(stream)
+    static Histogram histogram(LongStream stream, double binSize = 0.5, int binNum = 500) {
+        return UnivariateHistogram.buildUniform(0d, binSize * binNum, binSize).fill(stream.mapToDouble {
+            it / 1000 as double
+        })
     }
 
     static Values analyze(Map values = Collections.emptyMap(), NumassBlock block, Closure metaClosure = null) {
         return analyzer.analyze(block, Grind.buildMeta(values, metaClosure))
     }
-
-    static class Result {
-        double cr;
-        double crErr;
-        long num;
-        double t0;
-        int loChannel;
-        int upChannel;
-    }
+//
+//    static class Result {
+//        double cr;
+//        double crErr;
+//        long num;
+//        double t0;
+//        int loChannel;
+//        int upChannel;
+//    }
 }
diff --git a/numass-main/src/main/groovy/inr/numass/scripts/times/MultiPointHistogram.groovy b/numass-main/src/main/groovy/inr/numass/scripts/times/MultiPointHistogram.groovy
index 7aa3bce1..81b54aad 100644
--- a/numass-main/src/main/groovy/inr/numass/scripts/times/MultiPointHistogram.groovy
+++ b/numass-main/src/main/groovy/inr/numass/scripts/times/MultiPointHistogram.groovy
@@ -42,11 +42,11 @@ new GrindShell(ctx).eval {
     List<NumassPoint> points = loaders.collect { loader -> loader.optPoint(hv).get() }
 
     def loChannel = 400;
-    def upChannel = 800;
+    def upChannel = 2000;
 
-    def chain = new TimeAnalyzer().extendedEventStream(new MetaBlock(points), Grind.buildMeta("window.lo": loChannel, "window.up": upChannel))
+    def chain = new TimeAnalyzer().getEventsWithDelay(new MetaBlock(points), Grind.buildMeta("window.lo": loChannel, "window.up": upChannel)).mapToLong{it.value}
 
-    def histogram = PointAnalyzer.histogram(chain, 5e-6, 500).asTable();
+    def histogram = PointAnalyzer.histogram(chain, 1, 500).asTable();
 
     println "finished histogram calculation..."
 
diff --git a/numass-main/src/main/groovy/inr/numass/scripts/times/TestPointAnalyzer.groovy b/numass-main/src/main/groovy/inr/numass/scripts/times/TestPointAnalyzer.groovy
index 10296b54..46796b8f 100644
--- a/numass-main/src/main/groovy/inr/numass/scripts/times/TestPointAnalyzer.groovy
+++ b/numass-main/src/main/groovy/inr/numass/scripts/times/TestPointAnalyzer.groovy
@@ -8,6 +8,7 @@ import hep.dataforge.plots.fx.FXPlotManager
 import hep.dataforge.tables.ValueMap
 import inr.numass.NumassPlugin
 import inr.numass.data.PointAnalyzer
+import inr.numass.data.api.NumassAnalyzer
 import inr.numass.data.api.NumassPoint
 import inr.numass.data.api.NumassSet
 import inr.numass.data.storage.NumassStorage
@@ -29,8 +30,8 @@ new GrindShell(ctx).eval {
     NumassStorage storage = NumassStorageFactory.buildLocal(rootDir);
 
 
-    def set = "set_1"
-    def hv = 14500;
+    def set = "set_43"
+    def hv = 16000;
     def loader = storage.provide("loader::$set", NumassSet.class).get();
     def point = loader.provide("$hv", NumassPoint.class).get()
 
@@ -56,17 +57,9 @@ new GrindShell(ctx).eval {
 
     def t0 = (1..150).collect { 500 * it }
 
-//    point.blocks.eachWithIndex { block, index ->
-//        def statPlotPoints = t0.collect {
-//            def result = PointAnalyzer.analyze(block, t0: it, "window.lo": loChannel, "window.up": upChannel)
-//            ValueMap.ofMap("x": it / 1000, "y": result.getDouble("cr"), "y.err": result.getDouble("cr.err"));
-//        }
-//        plot.plot(name: index, frame: "stat-method", showLine: true, statPlotPoints)
-//    }
-
     def statPlotPoints = t0.collect {
         def result = PointAnalyzer.analyze(point, t0: it, "window.lo": loChannel, "window.up": upChannel)
-        ValueMap.ofMap("x": it / 1000, "y": result.getDouble("cr"), "y.err": result.getDouble("cr.err"));
+        ValueMap.ofMap("x": it / 1000, "y": result.getDouble("cr"), "y.err": result.getDouble(NumassAnalyzer.COUNT_RATE_ERROR_KEY));
     }
     plot.plot(name: "total", frame: "stat-method", showLine: true, statPlotPoints)
 
diff --git a/numass-main/src/main/groovy/inr/numass/scripts/times/TestProto.groovy b/numass-main/src/main/groovy/inr/numass/scripts/times/TestProto.groovy
index 81dc5af6..bbaf552f 100644
--- a/numass-main/src/main/groovy/inr/numass/scripts/times/TestProto.groovy
+++ b/numass-main/src/main/groovy/inr/numass/scripts/times/TestProto.groovy
@@ -8,6 +8,7 @@ import hep.dataforge.plots.fx.FXPlotManager
 import hep.dataforge.tables.ValueMap
 import inr.numass.NumassPlugin
 import inr.numass.data.PointAnalyzer
+import inr.numass.data.api.NumassAnalyzer
 import inr.numass.data.api.NumassPoint
 import inr.numass.data.storage.ProtoNumassPoint
 
@@ -19,7 +20,7 @@ ctx.pluginManager().load(NumassPlugin.class)
 
 new GrindShell(ctx).eval {
     PlotHelper plot = plots
-    NumassPoint point = ProtoNumassPoint.readFile(Paths.get("D:\\Work\\Numass\\data\\test\\40_kHz_5s.df"))
+    NumassPoint point = ProtoNumassPoint.readFile(Paths.get("D:\\Work\\Numass\\data\\2017_05\\Fill_3_events\\set_33\\p0(30s)(HV1=16000).df"))
 
     def loChannel = 0;
     def upChannel = 10000;
@@ -41,19 +42,12 @@ new GrindShell(ctx).eval {
 
     println "The expected count rate for 30 us delay is $trueCR"
 
-    def t0 = (1..150).collect { 500 * it }
+    def t0 = (1..150).collect { 1000 * it }
 
-//    point.blocks.eachWithIndex { block, index ->
-//        def statPlotPoints = t0.collect {
-//            def result = PointAnalyzer.analyze(block, t0: it, "window.lo": loChannel, "window.up": upChannel)
-//            ValueMap.ofMap("x": it / 1000, "y": result.getDouble("cr"), "y.err": result.getDouble("cr.err"));
-//        }
-//        plot.plot(name: index, frame: "stat-method", showLine: true, statPlotPoints)
-//    }
 
     def statPlotPoints = t0.collect {
         def result = PointAnalyzer.analyze(point, t0: it, "window.lo": loChannel, "window.up": upChannel)
-        ValueMap.ofMap("x": it / 1000, "y": result.getDouble("cr"), "y.err": result.getDouble("cr.err"));
+        ValueMap.ofMap("x": it / 1000, "y": result.getDouble("cr"), "y.err": result.getDouble(NumassAnalyzer.COUNT_RATE_ERROR_KEY));
     }
     plot.plot(name: "total", frame: "stat-method", showLine: true, thickness: 4, statPlotPoints)
 
diff --git a/numass-main/src/main/groovy/inr/numass/scripts/underflow/Underflow.groovy b/numass-main/src/main/groovy/inr/numass/scripts/underflow/Underflow.groovy
index 60158094..6236d855 100644
--- a/numass-main/src/main/groovy/inr/numass/scripts/underflow/Underflow.groovy
+++ b/numass-main/src/main/groovy/inr/numass/scripts/underflow/Underflow.groovy
@@ -6,10 +6,13 @@
 
 package inr.numass.scripts.underflow
 
+import hep.dataforge.cache.CachePlugin
 import hep.dataforge.context.Context
 import hep.dataforge.context.Global
-import hep.dataforge.grind.Grind
+import hep.dataforge.data.DataNode
+import hep.dataforge.data.DataSet
 import hep.dataforge.grind.GrindShell
+import hep.dataforge.grind.actions.GrindPipe
 import hep.dataforge.grind.helpers.PlotHelper
 import hep.dataforge.io.ColumnedDataWriter
 import hep.dataforge.meta.Meta
@@ -25,59 +28,84 @@ import inr.numass.data.NumassDataUtils
 import inr.numass.data.analyzers.TimeAnalyzer
 import inr.numass.data.api.NumassAnalyzer
 import inr.numass.data.api.NumassPoint
+import inr.numass.data.api.NumassSet
 import inr.numass.data.api.SimpleNumassPoint
 import inr.numass.data.storage.NumassStorage
 import inr.numass.data.storage.NumassStorageFactory
 
 import java.util.stream.Collectors
 
+import static hep.dataforge.grind.Grind.buildMeta
 import static inr.numass.data.api.NumassAnalyzer.CHANNEL_KEY
 import static inr.numass.data.api.NumassAnalyzer.COUNT_RATE_KEY
 
 Context ctx = Global.instance()
 ctx.pluginManager().load(FXPlotManager)
 ctx.pluginManager().load(NumassPlugin.class)
+ctx.pluginManager().load(CachePlugin.class)
+
+Meta meta = buildMeta {
+    data(dir: "D:\\Work\\Numass\\data\\2017_05\\Fill_2", mask: "set_.{1,3}")
+    generate(t0: 3e4, sort: true)
+    subtract(reference: 18600)
+    fit(xlow: 450, xHigh: 700, upper: 3100, binning: 20)
+}
+
 
 new GrindShell(ctx).eval {
 
     //Defining root directory
-    File dataDirectory = new File("D:\\Work\\Numass\\data\\2017_05\\Fill_2")
+    File dataDirectory = new File(meta.getString("data.dir"))
 
     //creating storage instance
 
     NumassStorage storage = NumassStorageFactory.buildLocal(dataDirectory);
 
     //Reading points
-    Map<Double, List<NumassPoint>> allPoints = StorageUtils
+    //Free operation. No reading done
+    List<NumassSet> sets = StorageUtils
             .loaderStream(storage)
-            .filter { it.key.matches("set_.{1,3}") }
+            .filter { it.key.matches(meta.getString("data.mask")) }
             .map {
         println "loading ${it.key}"
-        it.value
-    }.flatMap { it.points }
-            .collect(Collectors.groupingBy { it.voltage })
+        return it.value
+    }.collect(Collectors.toList());
 
-    Meta analyzerMeta = Grind.buildMeta(t0: 3e4)
-    NumassAnalyzer analyzer = new TimeAnalyzer()
+    NumassAnalyzer analyzer = new TimeAnalyzer();
 
-    //creating spectra
-    Map spectra = allPoints.collectEntries {
-        def point = new SimpleNumassPoint(it.key, it.value)
-        println "generating spectrum for ${point.voltage}"
-        return [(point.voltage): analyzer.getSpectrum(point, analyzerMeta)]
+    def dataBuilder = DataSet.builder(NumassPoint);
+
+    sets.sort { it.startTime }
+            .collectMany { it.points.collect() }
+            .groupBy { it.voltage }
+            .each { key, value ->
+                def point = new SimpleNumassPoint(key as double, value as List<NumassPoint>)
+                String name = (key as Integer).toString()
+                dataBuilder.putStatic(name, point, buildMeta(voltage: key));
+            }
+
+    DataNode<NumassPoint> data = dataBuilder.build()
+
+    def generate = GrindPipe.<NumassPoint, Table> build(name: "generate") {
+        return analyzer.getSpectrum(delegate.input as NumassPoint, delegate.meta)
     }
 
-
-
-    def refereceVoltage = 18600d
+    DataNode<Table> spectra = generate.run(context, data, meta.getMeta("generate"));
+    spectra = context.getFeature(CachePlugin).cacheNode("underflow", meta, spectra)
 
     //subtracting reference point
-    if (refereceVoltage) {
-        println "subtracting reference point ${refereceVoltage}"
-        def referencePoint = spectra[refereceVoltage]
-        spectra = spectra.findAll { it.key != refereceVoltage }.collectEntries {
-            return [(it.key): NumassDataUtils.subtractSpectrum(it.getValue() as Table, referencePoint as Table)]
+    Map<Double, Table> spectraMap
+    if (meta.hasValue("subtract.reference")) {
+        String referenceVoltage = meta["subtract.reference"].stringValue()
+        println "subtracting reference point ${referenceVoltage}"
+        def referencePoint = spectra.compute(referenceVoltage)
+        spectraMap = spectra
+                .findAll { it.name != referenceVoltage }
+                .collectEntries {
+            return [(it.meta["voltage"].doubleValue()): NumassDataUtils.subtractSpectrum(it.get(), referencePoint)]
         }
+    } else {
+        spectraMap = spectra.collectEntries { return [(it.meta["voltage"].doubleValue()): it.get()] }
     }
 
     //Showing selected points
@@ -97,22 +125,28 @@ new GrindShell(ctx).eval {
         //configuring and plotting
         plotGroup.configure(showLine: true, showSymbol: false, showErrors: false, connectionType: "step")
         def frame = (plots as PlotHelper).getManager().getPlotFrame("Spectra")
-        frame.configure("yAxis.type": "log")
+        frame.configureValue("yAxis.type", "log")
         frame.addAll(plotGroup)
     }
 
-    showPoints(spectra.findAll { it.key in [16200d, 16400d, 16800d, 17000d, 17200d, 17700d] })
-
-    println()
+    showPoints(spectraMap.findAll { it.key in [16200d, 16400d, 16800d, 17000d, 17200d, 17700d] })
 
     Table correctionTable = TableTransform.filter(
-            UnderflowFitter.fitAllPoints(spectra, 450, 700, 3100, 20),
+            UnderflowFitter.fitAllPoints(
+                    spectraMap,
+                    meta["fit.xlow"].intValue(),
+                    meta["fit.xHigh"].intValue(),
+                    meta["fit.upper"].intValue(),
+                    meta["fit.binning"].intValue()
+            ),
             "correction",
             0,
-            2)
+            2
+    )
+
     ColumnedDataWriter.writeTable(System.out, correctionTable, "underflow parameters")
 
     (plots as PlotHelper).plot(correctionTable, name: "correction", frame: "Correction") {
-        adapter("x.value":"U", "y.value":"correction")
+        adapter("x.value": "U", "y.value": "correction")
     }
 }
\ No newline at end of file