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package de.lmu.ifi.dbs.elki.visualization.visualizers.scatterplot.density;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2014
Ludwig-Maximilians-Universität München
Lehr- und Forschungseinheit für Datenbanksysteme
ELKI Development Team
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.awt.image.BufferedImage;
import java.util.Arrays;
import java.util.Collection;
import java.util.Comparator;
import org.apache.batik.util.SVGConstants;
import org.w3c.dom.Element;
import de.lmu.ifi.dbs.elki.database.ids.DBIDIter;
import de.lmu.ifi.dbs.elki.math.MathUtil;
import de.lmu.ifi.dbs.elki.math.MeanVariance;
import de.lmu.ifi.dbs.elki.result.HierarchicalResult;
import de.lmu.ifi.dbs.elki.result.KMLOutputHandler;
import de.lmu.ifi.dbs.elki.result.Result;
import de.lmu.ifi.dbs.elki.result.ResultUtil;
import de.lmu.ifi.dbs.elki.utilities.documentation.Reference;
import de.lmu.ifi.dbs.elki.visualization.VisualizationTask;
import de.lmu.ifi.dbs.elki.visualization.batikutil.ThumbnailRegistryEntry;
import de.lmu.ifi.dbs.elki.visualization.projections.CanvasSize;
import de.lmu.ifi.dbs.elki.visualization.projector.ScatterPlotProjector;
import de.lmu.ifi.dbs.elki.visualization.svg.SVGUtil;
import de.lmu.ifi.dbs.elki.visualization.visualizers.AbstractVisFactory;
import de.lmu.ifi.dbs.elki.visualization.visualizers.Visualization;
import de.lmu.ifi.dbs.elki.visualization.visualizers.scatterplot.AbstractScatterplotVisualization;
/**
* A simple density estimation visualization, based on a simple kernel-density
* <em>in the projection, not the actual data!</em>
*
* @author Erich Schubert
*
* @apiviz.stereotype factory
* @apiviz.uses Instance oneway - - «create»
*/
public class DensityEstimationOverlay extends AbstractVisFactory {
/**
* A short name characterizing this Visualizer.
*/
private static final String NAME = "Density estimation overlay";
/**
* Constructor.
*/
public DensityEstimationOverlay() {
super();
}
@Override
public Visualization makeVisualization(VisualizationTask task) {
return new Instance(task);
}
@Override
public void processNewResult(HierarchicalResult baseResult, Result result) {
Collection<ScatterPlotProjector<?>> ps = ResultUtil.filterResults(result, ScatterPlotProjector.class);
for(ScatterPlotProjector<?> p : ps) {
final VisualizationTask task = new VisualizationTask(NAME, p.getRelation(), p.getRelation(), this);
task.level = VisualizationTask.LEVEL_DATA + 1;
task.initDefaultVisibility(false);
baseResult.getHierarchy().add(p, task);
}
}
/**
* Instance for a particular data set.
*
* @author Erich Schubert
*/
// TODO: make parameterizable, in particular color map, kernel bandwidth and
// kernel function
public class Instance extends AbstractScatterplotVisualization {
/**
* Density map resolution
*/
private int resolution = 500;
/**
* The actual image
*/
private BufferedImage img = null;
/**
* Constructor.
*
* @param task Task
*/
public Instance(VisualizationTask task) {
super(task);
incrementalRedraw();
}
@Override
protected void redraw() {
if(img == null) {
renderImage();
}
CanvasSize canvas = proj.estimateViewport();
String imguri = ThumbnailRegistryEntry.INTERNAL_PREFIX + ThumbnailRegistryEntry.registerImage(img);
Element itag = svgp.svgElement(SVGConstants.SVG_IMAGE_TAG);
SVGUtil.setAtt(itag, SVGConstants.SVG_IMAGE_RENDERING_ATTRIBUTE, SVGConstants.SVG_OPTIMIZE_SPEED_VALUE);
SVGUtil.setAtt(itag, SVGConstants.SVG_X_ATTRIBUTE, canvas.minx);
SVGUtil.setAtt(itag, SVGConstants.SVG_Y_ATTRIBUTE, canvas.miny);
SVGUtil.setAtt(itag, SVGConstants.SVG_WIDTH_ATTRIBUTE, canvas.maxx - canvas.minx);
SVGUtil.setAtt(itag, SVGConstants.SVG_HEIGHT_ATTRIBUTE, canvas.maxy - canvas.miny);
SVGUtil.setAtt(itag, SVGConstants.SVG_STYLE_ATTRIBUTE, SVGConstants.CSS_OPACITY_PROPERTY + ": .5");
itag.setAttributeNS(SVGConstants.XLINK_NAMESPACE_URI, SVGConstants.XLINK_HREF_QNAME, imguri);
layer.appendChild(itag);
}
@Reference(authors = "D. W. Scott", title = "Multivariate density estimation: Theory, Practice, and Visualization", //
booktitle = "Multivariate Density Estimation: Theory, Practice, and Visualization", //
url = "http://dx.doi.org/10.1002/9780470316849")
private double[] initializeBandwidth(double[][] data) {
MeanVariance mv0 = new MeanVariance();
MeanVariance mv1 = new MeanVariance();
// For Kernel bandwidth.
for(double[] projected : data) {
mv0.put(projected[0]);
mv1.put(projected[1]);
}
// Set bandwidths according to Scott's rule:
// Note: in projected space, d=2.
double[] bandwidth = new double[2];
bandwidth[0] = MathUtil.SQRT5 * mv0.getSampleStddev() * Math.pow(rel.size(), -1 / 6.);
bandwidth[1] = MathUtil.SQRT5 * mv1.getSampleStddev() * Math.pow(rel.size(), -1 / 6.);
return bandwidth;
}
private void renderImage() {
// TODO: SAMPLE? Do region queries?
// Project the data just once, keep a copy.
double[][] data = new double[rel.size()][];
{
int i = 0;
for(DBIDIter iditer = rel.iterDBIDs(); iditer.valid(); iditer.advance()) {
data[i] = proj.fastProjectDataToRenderSpace(rel.get(iditer));
i++;
}
}
double[] bandwidth = initializeBandwidth(data);
// Compare by first component
Comparator<double[]> comp0 = new Comparator<double[]>() {
@Override
public int compare(double[] o1, double[] o2) {
return Double.compare(o1[0], o2[0]);
}
};
// Compare by second component
Comparator<double[]> comp1 = new Comparator<double[]>() {
@Override
public int compare(double[] o1, double[] o2) {
return Double.compare(o1[1], o2[1]);
}
};
// TODO: choose comparator order based on smaller bandwidth?
Arrays.sort(data, comp0);
CanvasSize canvas = proj.estimateViewport();
double min0 = canvas.minx, max0 = canvas.maxx, ste0 = (max0 - min0) / resolution;
double min1 = canvas.miny, max1 = canvas.maxy, ste1 = (max1 - min1) / resolution;
double kernf = 9. / (16 * bandwidth[0] * bandwidth[1]);
double maxdens = 0.0;
double[][] dens = new double[resolution][resolution];
{
// TODO: incrementally update the loff/roff values?
for(int x = 0; x < resolution; x++) {
double xlow = min0 + ste0 * x, xhig = xlow + ste0;
int loff = unflip(Arrays.binarySearch(data, new double[] { xlow - bandwidth[0] }, comp0));
int roff = unflip(Arrays.binarySearch(data, new double[] { xhig + bandwidth[0] }, comp0));
// Resort by second component
Arrays.sort(data, loff, roff, comp1);
for(int y = 0; y < resolution; y++) {
double ylow = min1 + ste1 * y, yhig = ylow + ste1;
int boff = unflip(Arrays.binarySearch(data, loff, roff, new double[] { 0, ylow - bandwidth[1] }, comp1));
int toff = unflip(Arrays.binarySearch(data, loff, roff, new double[] { 0, yhig + bandwidth[1] }, comp1));
for(int pos = boff; pos < toff; pos++) {
double[] val = data[pos];
double d0 = (val[0] < xlow) ? (xlow - val[0]) : (val[0] > xhig) ? (val[0] - xhig) : 0;
double d1 = (val[1] < ylow) ? (ylow - val[1]) : (val[1] > yhig) ? (val[1] - yhig) : 0;
d0 = d0 / bandwidth[0];
d1 = d1 / bandwidth[1];
dens[x][y] += kernf * (1 - d0 * d0) * (1 - d1 * d1);
}
maxdens = Math.max(maxdens, dens[x][y]);
}
// Restore original sorting, as the intervals overlap
Arrays.sort(data, loff, roff, comp0);
}
}
img = new BufferedImage(resolution, resolution, BufferedImage.TYPE_INT_ARGB);
{
for(int x = 0; x < resolution; x++) {
for(int y = 0; y < resolution; y++) {
int rgb = KMLOutputHandler.getColorForValue(dens[x][y] / maxdens).getRGB();
img.setRGB(x, y, rgb);
}
}
}
}
private int unflip(int binarySearch) {
if(binarySearch < 0) {
return (-binarySearch) - 1;
}
else {
return binarySearch;
}
}
}
}
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