add logarithmic scaling for the y-axis

Often we have a few very high values and a lot
low values. With a linearly scaled y-axis the
plot is mostly useless.

pdb-plotting/src/main/java/org/lucares/recommind/logs/GnuplotFileGenerator.java

@@ -2,6 +2,8 @@ package org.lucares.recommind.logs;
 
 import java.util.Collection;
 
+import org.lucares.pdb.plot.api.AxisScale;
+
 public class GnuplotFileGenerator {
 
 	public String generate(final GnuplotSettings settings, final Collection<DataSeries> dataSeries) {
@@ -20,6 +22,11 @@ public class GnuplotFileGenerator {
 		appendfln(result, "set xtics rotate by %d", settings.getRotateXAxisLabel());
 
 		appendfln(result, "set ylabel \"%s\"", settings.getYlabel());
+		if (settings.getYAxisScale() == AxisScale.LOG10) {
+			appendfln(result, "set logscale y");
+		} else if (settings.getYAxisScale() == AxisScale.LOG2) {
+			appendfln(result, "set logscale y 2");
+		}
 
 		appendfln(result, "set output \"%s\"", settings.getOutput().toAbsolutePath().toString().replace("\\", "/"));
 		appendf(result, "plot ");

pdb-plotting/src/main/java/org/lucares/recommind/logs/GnuplotSettings.java

@@ -2,6 +2,8 @@ package org.lucares.recommind.logs;
 
 import java.nio.file.Path;
 
+import org.lucares.pdb.plot.api.AxisScale;
+
 public class GnuplotSettings {
 	private String terminal = "png";
 	private int height = 1200;
@@ -25,6 +27,7 @@ public class GnuplotSettings {
 
 	// set xtics rotate by 80
 	private int rotateXAxisLabel = -80;
+	private AxisScale yAxisScale;
 
 	public GnuplotSettings(final Path output) {
 		this.output = output;
@@ -106,6 +109,14 @@ public class GnuplotSettings {
 		return output;
 	}
 
+	public void setYAxisScale(final AxisScale yAxisScale) {
+		this.yAxisScale = yAxisScale;
+	}
+
+	public AxisScale getYAxisScale() {
+		return yAxisScale;
+	}
+
 	// plot 'sample.txt' using 1:2 title 'Bytes' with linespoints 2
 
 }

pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java

@@ -110,6 +110,7 @@ public class Plotter {
 			gnuplotSettings.setHeight(height);
 			gnuplotSettings.setWidth(width);
 			gnuplotSettings.setFormatX(getFormatX(minDate, maxDate));
+			gnuplotSettings.setYAxisScale(plotSettings.getYAxisScale());
 			gnuplot.plot(gnuplotSettings, dataSeries);
 
 			return new PlotResult(outputFile.getFileName(), dataSeries);