Mercurial > dive4elements > gnv-client
view gnv-artifacts/src/main/java/de/intevation/gnv/math/XYColumn.java @ 1030:c07d9f9a738c
Removed bugs that existed in the caching mechanism (issue264, issue268).
gnv-artifacts/trunk@1067 c6561f87-3c4e-4783-a992-168aeb5c3f6f
author | Ingo Weinzierl <ingo.weinzierl@intevation.de> |
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date | Thu, 06 May 2010 08:32:56 +0000 |
parents | 05bf8534a35a |
children | f953c9a559d8 |
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package de.intevation.gnv.math; import java.util.ArrayList; import java.util.Collections; import java.util.List; import org.apache.commons.math.FunctionEvaluationException; import org.apache.commons.math.MathException; import org.apache.commons.math.analysis.UnivariateRealFunction; import org.apache.commons.math.analysis.interpolation.SplineInterpolator; import org.apache.commons.math.analysis.interpolation.UnivariateRealInterpolator; import org.apache.log4j.Logger; /** * A column of discrete attributed height values located at a point. * Values between the discrete height values are interpolated. * * @author <a href="mailto:ingo.weinzierl@intevation.de">Ingo Weinzierl</a> * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a> */ public class XYColumn extends Point2d implements UnivariateRealFunction { private static Logger log = Logger.getLogger(XYColumn.class); /** * The list of discrete height values. */ protected List<HeightValue> values; /** * The curve used to interpolate the points between the * discrete height values. */ protected transient UnivariateRealFunction curve; /** * Default constructor. */ public XYColumn() { values = new ArrayList<HeightValue>(); } /** * Constructor to create an XYColumn with a given (x, y) coordinate * and an (i, j) index tuple. * @param x The x coordinate. * @param y The y coordinate. * @param i The i component. * @param j The j component. */ public XYColumn(double x, double y, int i, int j) { super(x, y, i, j); values = new ArrayList<HeightValue>(); } /** * Adds a given height value to the list of height values. * @param value The height value. */ public void add(HeightValue value) { values.add(value); } /** * Returns the list of height values. * @return The list of height values. */ public List<HeightValue> getValues() { return values; } public double value(double depth) { try { if (curve != null) { HeightValue h = values.get(0); // extrapolate beyond boundaries by repeating if (depth > h.z) return h.v; h = values.get(values.size()-1); if (depth < h.z) return h.v; return curve.value(depth); } } catch (FunctionEvaluationException fee) { log.error("evaluation failed", fee); } return Double.NaN; } /** * Prepares this XYColumn to be queried. A given XYDepth * object is used to fill the values to a certain depth. * @param xyDepth To figure out the depth a the cordinate. * @return true if preparation succeeds else false. */ public boolean prepare(XYDepth xyDepth) { if (curve == null) { int N = values.size(); if (N == 0) { log.error("no points for interpolation"); return false; } if (N == 1) { // only one value -> constant function curve = new ConstantFunction(values.get(0).v); } else { // more than on value double depth = xyDepth.depth(this); Collections.sort(values, HeightValue.INV_Z_COMPARATOR); // if there is no value at 0 repeat first value HeightValue first = values.get(0); if (first.z < 0d) { values.add(0, new HeightValue(0d, first.v, first.k-1)); ++N; } // if there is no value at depth repeat last value HeightValue last = values.get(N-1); if (last.z > depth) { values.add(new HeightValue(depth, last.v, last.k+1)); ++N; } if (N < 3) { // interpolate linear first = values.get(0); last = values.get(N-1); curve = new LinearFunction.Univariate( first.z, first.v, last.z, last.v); } else { // higher degree interpolation double [] z = new double[N]; double [] v = new double[N]; for (int i = 0; i < N; ++i) { HeightValue h = values.get(N-1-i); z[i] = h.z; v[i] = h.v; } try { curve = getInterpolator().interpolate(z, v); } catch (MathException me) { log.error("interpolation failed", me); return false; } } } } return true; } /** * Returns the interpolator used to interpolate the values between * the discrete height values. This class returns an instance of * {@link org.apache.commons.math.analysis.interpolation.SplineInterpolator}. * Override this if you want to use another kind of interpolation. * @return The interpolator to be used. */ protected UnivariateRealInterpolator getInterpolator() { return new SplineInterpolator(); } } // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :