Author: erans
Date: Sat Aug 18 01:09:25 2012
New Revision: 1374492
URL: http://svn.apache.org/viewvc?rev=1374492&view=rev
Log:
Code cleanup: Moved all computations to the constructor, allowing the class
to be immutable.
Modified:
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/optimization/fitting/GaussianFitter.java
Modified:
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/optimization/fitting/GaussianFitter.java
URL:
http://svn.apache.org/viewvc/commons/proper/math/trunk/src/main/java/org/apache/commons/math3/optimization/fitting/GaussianFitter.java?rev=1374492&r1=1374491&r2=1374492&view=diff
==============================================================================
---
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/optimization/fitting/GaussianFitter.java
(original)
+++
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/optimization/fitting/GaussianFitter.java
Sat Aug 18 01:09:25 2012
@@ -30,6 +30,7 @@ import org.apache.commons.math3.exceptio
import
org.apache.commons.math3.optimization.DifferentiableMultivariateVectorOptimizer;
import org.apache.commons.math3.optimization.fitting.CurveFitter;
import org.apache.commons.math3.optimization.fitting.WeightedObservedPoint;
+import org.apache.commons.math3.util.FastMath;
/**
* Fits points to a {@link
@@ -127,15 +128,22 @@ public class GaussianFitter extends Curv
* based on the specified observed points.
*/
public static class ParameterGuesser {
- /** Observed points. */
- private final WeightedObservedPoint[] observations;
- /** Resulting guessed parameters. */
- private double[] parameters;
+ /** Normalization factor. */
+ private final double norm;
+ /** Mean. */
+ private final double mean;
+ /** Standard deviation. */
+ private final double sigma;
/**
* Constructs instance with the specified observed points.
*
- * @param observations observed points upon which should base guess
+ * @param observations Observed points from which to guess the
+ * parameters of the Gaussian.
+ * @throws NullArgumentException if {@code observations} is
+ * {@code null}.
+ * @throws NumberIsTooSmallException if there are less than 3
+ * observations.
*/
public ParameterGuesser(WeightedObservedPoint[] observations) {
if (observations == null) {
@@ -144,47 +152,101 @@ public class GaussianFitter extends Curv
if (observations.length < 3) {
throw new NumberIsTooSmallException(observations.length, 3,
true);
}
- this.observations = observations.clone();
+
+ final WeightedObservedPoint[] sorted =
sortObservations(observations);
+ final double[] params = basicGuess(sorted);
+
+ norm = params[0];
+ mean = params[1];
+ sigma = params[2];
}
/**
- * Guesses the parameters based on the observed points.
+ * Gets an estimation of the parameters.
*
- * @return the guessed parameters: norm, mean and sigma.
+ * @return the guessed parameters, in the following order:
+ * <ul>
+ * <li>Normalization factor</li>
+ * <li>Mean</li>
+ * <li>Standard deviation</li>
+ * </ul>
*/
public double[] guess() {
- if (parameters == null) {
- parameters = basicGuess(observations);
- }
- return parameters.clone();
+ return new double[] { norm, mean, sigma };
+ }
+
+ /**
+ * Sort the observations.
+ *
+ * @param unsorted Input observations.
+ * @return the input observations, sorted.
+ */
+ private WeightedObservedPoint[]
sortObservations(WeightedObservedPoint[] unsorted) {
+ final WeightedObservedPoint[] observations = unsorted.clone();
+ final Comparator<WeightedObservedPoint> cmp
+ = new Comparator<WeightedObservedPoint>() {
+ public int compare(WeightedObservedPoint p1,
+ WeightedObservedPoint p2) {
+ if (p1 == null && p2 == null) {
+ return 0;
+ }
+ if (p1 == null) {
+ return -1;
+ }
+ if (p2 == null) {
+ return 1;
+ }
+ if (p1.getX() < p2.getX()) {
+ return -1;
+ }
+ if (p1.getX() > p2.getX()) {
+ return 1;
+ }
+ if (p1.getY() < p2.getY()) {
+ return -1;
+ }
+ if (p1.getY() > p2.getY()) {
+ return 1;
+ }
+ if (p1.getWeight() < p2.getWeight()) {
+ return -1;
+ }
+ if (p1.getWeight() > p2.getWeight()) {
+ return 1;
+ }
+ return 0;
+ }
+ };
+
+ Arrays.sort(observations, cmp);
+ return observations;
}
/**
* Guesses the parameters based on the specified observed points.
*
- * @param points Observed points upon which should base guess.
- * @return the guessed parameters: norm, mean and sigma.
+ * @param points Observed points, sorted.
+ * @return the guessed parameters (normalization factor, mean and
+ * sigma).
*/
private double[] basicGuess(WeightedObservedPoint[] points) {
- Arrays.sort(points, createWeightedObservedPointComparator());
- double[] params = new double[3];
-
- int maxYIdx = findMaxY(points);
- params[0] = points[maxYIdx].getY();
- params[1] = points[maxYIdx].getX();
+ final int maxYIdx = findMaxY(points);
+ final double n = points[maxYIdx].getY();
+ final double m = points[maxYIdx].getX();
double fwhmApprox;
try {
- double halfY = params[0] + ((params[1] - params[0]) / 2.0);
- double fwhmX1 = interpolateXAtY(points, maxYIdx, -1, halfY);
- double fwhmX2 = interpolateXAtY(points, maxYIdx, +1, halfY);
+ final double halfY = n + ((m - n) / 2);
+ final double fwhmX1 = interpolateXAtY(points, maxYIdx, -1,
halfY);
+ final double fwhmX2 = interpolateXAtY(points, maxYIdx, 1,
halfY);
fwhmApprox = fwhmX2 - fwhmX1;
} catch (OutOfRangeException e) {
+ // TODO: Exceptions should not be used for flow control.
fwhmApprox = points[points.length - 1].getX() -
points[0].getX();
}
- params[2] = fwhmApprox / (2.0 * Math.sqrt(2.0 * Math.log(2.0)));
+ final double s = fwhmApprox / (2 * FastMath.sqrt(2 *
FastMath.log(2)));
- return params;
+ return new double[] { n, m, s };
}
/**
@@ -208,33 +270,35 @@ public class GaussianFitter extends Curv
* specified Y.
*
* @param points Points to use for interpolation.
- * @param startIdx Index within points from which to start search for
- * interpolation bounds points.
- * @param idxStep Index step for search for interpolation bounds
points.
+ * @param startIdx Index within points from which to start the search
for
+ * interpolation bounds points.
+ * @param idxStep Index step for searching interpolation bounds points.
* @param y Y value for which X should be determined.
- * @return the value of X at the specified Y.
+ * @return the value of X for the specified Y.
* @throws ZeroException if {@code idxStep} is 0.
* @throws OutOfRangeException if specified {@code y} is not within the
* range of the specified {@code points}.
*/
private double interpolateXAtY(WeightedObservedPoint[] points,
- int startIdx, int idxStep, double y)
+ int startIdx,
+ int idxStep,
+ double y)
throws OutOfRangeException {
if (idxStep == 0) {
throw new ZeroException();
}
- WeightedObservedPoint[] twoPoints =
getInterpolationPointsForY(points, startIdx, idxStep, y);
- WeightedObservedPoint pointA = twoPoints[0];
- WeightedObservedPoint pointB = twoPoints[1];
- if (pointA.getY() == y) {
- return pointA.getX();
+ final WeightedObservedPoint[] twoPoints
+ = getInterpolationPointsForY(points, startIdx, idxStep, y);
+ final WeightedObservedPoint p1 = twoPoints[0];
+ final WeightedObservedPoint p2 = twoPoints[1];
+ if (p1.getY() == y) {
+ return p1.getX();
}
- if (pointB.getY() == y) {
- return pointB.getX();
+ if (p2.getY() == y) {
+ return p2.getX();
}
- return pointA.getX() +
- (((y - pointA.getY()) * (pointB.getX() - pointA.getX())) /
- (pointB.getY() - pointA.getY()));
+ return p1.getX() + (((y - p1.getY()) * (p2.getX() - p1.getX())) /
+ (p2.getY() - p1.getY()));
}
/**
@@ -253,84 +317,50 @@ public class GaussianFitter extends Curv
* range of the specified {@code points}.
*/
private WeightedObservedPoint[]
getInterpolationPointsForY(WeightedObservedPoint[] points,
- int
startIdx, int idxStep, double y)
+ int
startIdx,
+ int idxStep,
+ double y)
throws OutOfRangeException {
if (idxStep == 0) {
throw new ZeroException();
}
for (int i = startIdx;
- (idxStep < 0) ? (i + idxStep >= 0) : (i + idxStep <
points.length);
+ idxStep < 0 ? i + idxStep >= 0 : i + idxStep < points.length;
i += idxStep) {
- if (isBetween(y, points[i].getY(), points[i +
idxStep].getY())) {
- return (idxStep < 0) ?
- new WeightedObservedPoint[] { points[i + idxStep],
points[i] } :
- new WeightedObservedPoint[] { points[i], points[i +
idxStep] };
+ final WeightedObservedPoint p1 = points[i];
+ final WeightedObservedPoint p2 = points[i + idxStep];
+ if (isBetween(y, p1.getY(), p2.getY())) {
+ if (idxStep < 0) {
+ return new WeightedObservedPoint[] { p2, p1 };
+ } else {
+ return new WeightedObservedPoint[] { p1, p2 };
+ }
}
}
- double minY = Double.POSITIVE_INFINITY;
- double maxY = Double.NEGATIVE_INFINITY;
- for (final WeightedObservedPoint point : points) {
- minY = Math.min(minY, point.getY());
- maxY = Math.max(maxY, point.getY());
- }
- throw new OutOfRangeException(y, minY, maxY);
+ // Boundaries are replaced by dummy values because the raised
+ // exception is caught and the message never displayed.
+ // TODO: Exceptions should not be used for flow control.
+ throw new OutOfRangeException(y,
+ Double.NEGATIVE_INFINITY,
+ Double.POSITIVE_INFINITY);
}
/**
* Determines whether a value is between two other values.
*
- * @param value Value to determine whether is between {@code boundary1}
+ * @param value Value to test whether it is between {@code boundary1}
* and {@code boundary2}.
* @param boundary1 One end of the range.
* @param boundary2 Other end of the range.
* @return {@code true} if {@code value} is between {@code boundary1}
and
* {@code boundary2} (inclusive), {@code false} otherwise.
*/
- private boolean isBetween(double value, double boundary1, double
boundary2) {
+ private boolean isBetween(double value,
+ double boundary1,
+ double boundary2) {
return (value >= boundary1 && value <= boundary2) ||
- (value >= boundary2 && value <= boundary1);
- }
-
- /**
- * Factory method creating {@code Comparator} for comparing
- * {@code WeightedObservedPoint} instances.
- *
- * @return the new {@code Comparator} instance.
- */
- private Comparator<WeightedObservedPoint>
createWeightedObservedPointComparator() {
- return new Comparator<WeightedObservedPoint>() {
- public int compare(WeightedObservedPoint p1,
WeightedObservedPoint p2) {
- if (p1 == null && p2 == null) {
- return 0;
- }
- if (p1 == null) {
- return -1;
- }
- if (p2 == null) {
- return 1;
- }
- if (p1.getX() < p2.getX()) {
- return -1;
- }
- if (p1.getX() > p2.getX()) {
- return 1;
- }
- if (p1.getY() < p2.getY()) {
- return -1;
- }
- if (p1.getY() > p2.getY()) {
- return 1;
- }
- if (p1.getWeight() < p2.getWeight()) {
- return -1;
- }
- if (p1.getWeight() > p2.getWeight()) {
- return 1;
- }
- return 0;
- }
- };
+ (value >= boundary2 && value <= boundary1);
}
}
}
