diff --git a/pdb-plotting/src/main/java/org/lucares/recommind/logs/DataSeries.java b/pdb-plotting/src/main/java/org/lucares/recommind/logs/DataSeries.java
index fe183b7..77abca7 100644
--- a/pdb-plotting/src/main/java/org/lucares/recommind/logs/DataSeries.java
+++ b/pdb-plotting/src/main/java/org/lucares/recommind/logs/DataSeries.java
@@ -11,22 +11,17 @@ public class DataSeries {
 
 	private final Integer pointType;
 
-	public DataSeries(final File dataFile, final String title) {
+	private final int values;
+
+	public DataSeries(final File dataFile, final String title, final int values) {
 		super();
 		this.dataFile = dataFile;
 		this.title = title;
+		this.values = values;
 		this.color = null;
 		this.pointType = null;
 	}
 
-	public DataSeries(final File dataFile, final String title, final GnuplotColor color, final Integer pointType) {
-		super();
-		this.dataFile = dataFile;
-		this.title = title;
-		this.color = color;
-		this.pointType = pointType;
-	}
-
 	public GnuplotColor getColor() {
 		return color;
 	}
@@ -42,4 +37,8 @@ public class DataSeries {
 	public String getTitle() {
 		return title;
 	}
+
+	public int getValues() {
+		return values;
+	}
 }
diff --git a/pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java b/pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java
index e63614b..3d7a61e 100644
--- a/pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java
+++ b/pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java
@@ -17,7 +17,11 @@ import java.util.Iterator;
 import java.util.stream.Stream;
 
 import org.lucares.pdb.api.Entry;
+import org.lucares.pdb.api.GroupResult;
+import org.lucares.pdb.api.Result;
+import org.lucares.pdb.api.Tags;
 import org.lucares.performance.db.FileUtils;
+import org.lucares.performance.db.Grouping;
 import org.lucares.performance.db.PerformanceDb;
 
 public class Plotter {
@@ -43,17 +47,24 @@ public class Plotter {
 		return outputDir;
 	}
 
-	public File plot(final String query, final int height, final int width) throws InternalPlottingException {
+	public File plot(final String query, final int height, final int width, final String groupBy)
+			throws InternalPlottingException {
 		try {
 			final Collection<DataSeries> dataSeries = new ArrayList<>();
 
-			final Stream<Entry> entries = db.get(query).singleGroup().asStream();
+			final Result result = db.get(query, groupBy);
 
-			final File dataFile = File.createTempFile("data", ".dat", tmpBaseDir.toFile());
-			final DataSeries dataSerie = new DataSeries(dataFile, query);
-			toCsv(entries, dataFile);
+			for (final GroupResult groupResult : result.getGroups()) {
 
-			dataSeries.add(dataSerie);
+				final Stream<Entry> entries = groupResult.asStream();
+
+				final File dataFile = File.createTempFile("data", ".dat", tmpBaseDir.toFile());
+				final int values = toCsv(entries, dataFile);
+
+				final String title = title(groupResult.getGroupedBy(), values);
+				final DataSeries dataSerie = new DataSeries(dataFile, title, values);
+				dataSeries.add(dataSerie);
+			}
 
 			final File outputFile = File.createTempFile("out", ".png", outputDir.toFile());
 			final Gnuplot gnuplot = new Gnuplot(tmpBaseDir);
@@ -70,6 +81,23 @@ public class Plotter {
 		}
 	}
 
+	private String title(final Tags tags, final int values) {
+
+		final StringBuilder result = new StringBuilder();
+
+		assert tags.getKeys().size() <= 1;
+		tags.forEach((k, v) -> {
+			result.append(v);
+		});
+
+		result.append("(");
+		result.append(values);
+		result.append(")");
+
+		return result.toString();
+
+	}
+
 	public static void main(final String[] args) throws Exception {
 		final Path dataDirectory = Paths.get(args[0]);
 		final Path outputDirectory = Paths.get(args[1]);
@@ -81,7 +109,7 @@ public class Plotter {
 
 			try (PerformanceDb db = new PerformanceDb(dataDirectory)) {
 				final Plotter plotter = new Plotter(db, tmpBaseDir, outputDirectory);
-				final File image = plotter.plot(query, 1600, 1200);
+				final File image = plotter.plot(query, 1600, 1200, Grouping.NO_GROUPING);
 				System.out.println("plotted image: " + image);
 			}
 
@@ -90,7 +118,7 @@ public class Plotter {
 		}
 	}
 
-	private static void toCsv(final Stream<Entry> entries, final File dataFile) throws IOException {
+	private static int toCsv(final Stream<Entry> entries, final File dataFile) throws IOException {
 
 		final long start = System.nanoTime();
 		int count = 0;
@@ -111,6 +139,8 @@ public class Plotter {
 				count++;
 			}
 		}
+
 		System.out.println("wrote " + count + " values to csv in: " + (System.nanoTime() - start) / 1_000_000.0 + "ms");
+		return count;
 	}
 }
diff --git a/pdb-ui/src/main/java/org/lucares/pdbui/PdbController.java b/pdb-ui/src/main/java/org/lucares/pdbui/PdbController.java
index 8d60b76..ba63f80 100644
--- a/pdb-ui/src/main/java/org/lucares/pdbui/PdbController.java
+++ b/pdb-ui/src/main/java/org/lucares/pdbui/PdbController.java
@@ -50,7 +50,7 @@ public class PdbController implements HardcodedValues, CollectionUtils {
 			final int width = request.getWidth();
 
 			System.out.println(query);
-			final File image = plotter.plot(query, height, width);
+			final File image = plotter.plot(query, height, width, request.getGroupBy());
 
 			final Path relativeImagePath = plotter.getOutputDir().relativize(image.toPath());
 			return new PlotResponse(WEB_IMAGE_OUTPUT_PATH + "/" + relativeImagePath.toString());
@@ -88,6 +88,26 @@ public class PdbController implements HardcodedValues, CollectionUtils {
 		}
 	}
 
+	@RequestMapping(path = "/fields", //
+			method = RequestMethod.GET, //
+			consumes = MediaType.APPLICATION_JSON_UTF8_VALUE, //
+			produces = MediaType.APPLICATION_JSON_UTF8_VALUE //
+	)
+	@ResponseBody
+	List<String> fields() {
+
+		try {
+
+			final List<String> fields = db.getDb().getFields();
+
+			return fields;
+
+		} catch (final Exception e) {
+			e.printStackTrace();
+			throw new InternalServerError(e);
+		}
+	}
+
 	private List<AutocompleteProposal> toAutocompleteProposals(final List<Proposal> proposals) {
 
 		final List<AutocompleteProposal> result = new ArrayList<>();
diff --git a/pdb-ui/src/main/java/org/lucares/pdbui/domain/PlotRequest.java b/pdb-ui/src/main/java/org/lucares/pdbui/domain/PlotRequest.java
index efabdbb..3e29926 100644
--- a/pdb-ui/src/main/java/org/lucares/pdbui/domain/PlotRequest.java
+++ b/pdb-ui/src/main/java/org/lucares/pdbui/domain/PlotRequest.java
@@ -7,6 +7,8 @@ public class PlotRequest {
 
 	private int width;
 
+	private String groupBy;
+
 	public String getQuery() {
 		return query;
 	}
@@ -35,4 +37,12 @@ public class PlotRequest {
 	public String toString() {
 		return query + ":" + height + "x" + width;
 	}
+
+	public String getGroupBy() {
+		return groupBy;
+	}
+
+	public void setGroupBy(final String groupBy) {
+		this.groupBy = groupBy;
+	}
 }
diff --git a/pdb-ui/src/main/resources/resources/index.html b/pdb-ui/src/main/resources/resources/index.html
index 41aaddd..e0fcdb2 100644
--- a/pdb-ui/src/main/resources/resources/index.html
+++ b/pdb-ui/src/main/resources/resources/index.html
@@ -20,6 +20,8 @@
 				<input id="search-input" data-autocomplete="autocomplete"
 					data-autocomplete-empty-message="nothing found" />
 			</div>
+			<div id="search-group-by">
+			</div>
 			<button id="search-submit"><i class="fa fa-search"> Search</i></button>
 		</div>
 		<div id="result-view">
diff --git a/pdb-ui/src/main/resources/resources/js/search.js b/pdb-ui/src/main/resources/resources/js/search.js
index 8f4f5f2..24e904c 100644
--- a/pdb-ui/src/main/resources/resources/js/search.js
+++ b/pdb-ui/src/main/resources/resources/js/search.js
@@ -3,6 +3,8 @@ $(document).ready(function(){
 
 	$('#search-submit').click(plot);
 	
+	initGroupBy();
+	
 	AutoComplete({
 		HttpMethod: "GET",
 		Delay: 300,
@@ -27,6 +29,24 @@ $(document).ready(function(){
 	});
 });
 
+function initGroupBy()
+{
+	var successCallback = function (response) {
+	
+		response.forEach(function(item, index){
+			$('#search-group-by').append('<input type="radio" id="groupBy-'+index+'" name="groupBy" value="'+item+'" /><label for="groupBy-'+index+'">'+item+'</label>');
+		});
+	
+	};
+	
+	var errorCallback = function (){
+		$('#result-view').text("FAILED: " + JSON.stringify(e));
+	};
+
+	getJson("fields", {}, successCallback, errorCallback)
+	
+}
+
 function showLoadingIcon()
 {
 	$('#result-view').html("<div class='center'><div class='uil-cube-css' style='-webkit-transform:scale(0.41)'><div /><div></div><div></div><div></div></div></div>");
@@ -41,6 +61,7 @@ function plot(event){
 	request['query'] = $('#search-input').val();
 	request['height'] = $('#result-view').height()-10;
 	request['width'] = $('#result-view').width()-10;
+	request['groupBy'] = $('input[name=groupBy]:checked').val();
 	
 	var success = function(response){
 			
@@ -67,4 +88,15 @@ function postJson(url, requestData, successCallback, errorCallback) {
 		.fail(errorCallback);
 }
 
+function getJson(url, requestData, successCallback, errorCallback) {
+
+	$.ajax({
+			type: "GET",
+			url: url,
+			data: requestData,
+			contentType: 'application/json'
+		})
+		.done(successCallback)
+		.fail(errorCallback);
+}
 
diff --git a/performanceDb/src/main/java/org/lucares/performance/db/Grouping.java b/performanceDb/src/main/java/org/lucares/performance/db/Grouping.java
index 506f6dc..a6b54cc 100644
--- a/performanceDb/src/main/java/org/lucares/performance/db/Grouping.java
+++ b/performanceDb/src/main/java/org/lucares/performance/db/Grouping.java
@@ -11,6 +11,7 @@ import org.lucares.pdb.api.Tags;
 public class Grouping {
 
 	public static final String NO_GROUPING = null;
+	public static final String DEFAULT_GROUP = "<default>";
 	private final List<Group> groups = new ArrayList<>();
 
 	private Grouping(final Group group) {
@@ -25,7 +26,7 @@ public class Grouping {
 
 		final Grouping result;
 		if (groupByField == NO_GROUPING) {
-			final Group group = new Group(null, pdbReaders);
+			final Group group = new Group(Tags.EMPTY, pdbReaders);
 
 			result = new Grouping(group);
 		} else {
@@ -35,10 +36,10 @@ public class Grouping {
 				final Tags tags = pdbReader.getPdbFile().getTags();
 				final String value = tags.getValue(groupByField);
 
-				if (value != null) {
-					addIfNotExists(grouping, groupByField, value);
-					grouping.get(value).addReader(pdbReader);
-				}
+				final String groupName = value != null ? value : DEFAULT_GROUP;
+
+				addIfNotExists(grouping, groupByField, groupName);
+				grouping.get(groupName).addReader(pdbReader);
 			}
 			result = new Grouping(grouping.values());
 		}
diff --git a/performanceDb/src/main/java/org/lucares/performance/db/PerformanceDb.java b/performanceDb/src/main/java/org/lucares/performance/db/PerformanceDb.java
index d7ad7e2..2961c24 100644
--- a/performanceDb/src/main/java/org/lucares/performance/db/PerformanceDb.java
+++ b/performanceDb/src/main/java/org/lucares/performance/db/PerformanceDb.java
@@ -15,6 +15,7 @@ import java.util.logging.Logger;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 
+import org.lucares.ludb.Field;
 import org.lucares.ludb.H2DB;
 import org.lucares.ludb.Proposal;
 import org.lucares.pdb.api.Entry;
@@ -22,7 +23,7 @@ import org.lucares.pdb.api.GroupResult;
 import org.lucares.pdb.api.Result;
 import org.lucares.pdb.api.Tags;
 
-public class PerformanceDb implements AutoCloseable {
+public class PerformanceDb implements AutoCloseable, CollectionUtils {
 	private static final Logger LOGGER = Logger.getLogger(PerformanceDb.class.getCanonicalName());
 
 	private final TagsToFile tagsToFile;
@@ -178,4 +179,10 @@ public class PerformanceDb implements AutoCloseable {
 	public List<Proposal> autocomplete(final String query, final int caretIndex) {
 		return db.proposeTagForQuery(query, caretIndex);
 	}
+
+	public List<String> getFields() {
+		final List<Field> fields = db.getAvailableFields("");
+
+		return map(fields, Field::getName);
+	}
 }