ingo@427: package de.intevation.gnv.math;
ingo@427:
ingo@427: import java.util.ArrayList;
sascha@779: import java.util.Collections;
ingo@427: import java.util.List;
sascha@779:
sascha@779: import org.apache.commons.math.FunctionEvaluationException;
sascha@779: import org.apache.commons.math.MathException;
sascha@779:
sascha@779: import org.apache.commons.math.analysis.UnivariateRealFunction;
sascha@433:
sascha@433: import org.apache.commons.math.analysis.interpolation.SplineInterpolator;
sascha@433: import org.apache.commons.math.analysis.interpolation.UnivariateRealInterpolator;
sascha@433:
sascha@433: import org.apache.log4j.Logger;
ingo@427:
ingo@427: /**
sascha@807: * A column of discrete attributed height values located at a point.
sascha@807: * Values between the discrete height values are interpolated.
sascha@807: *
sascha@780: * @author <a href="mailto:ingo.weinzierl@intevation.de">Ingo Weinzierl</a>
sascha@780: * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a>
ingo@427: */
ingo@429: public class XYColumn
sascha@431: extends Point2d
sascha@433: implements UnivariateRealFunction
ingo@429: {
sascha@434: private static Logger log = Logger.getLogger(XYColumn.class);
sascha@433:
sascha@807: /**
sascha@807: * The list of discrete height values.
sascha@807: */
sascha@432: protected List<HeightValue> values;
ingo@427:
sascha@807: /**
sascha@807: * The curve used to interpolate the points between the
sascha@807: * discrete height values.
sascha@807: */
sascha@433: protected transient UnivariateRealFunction curve;
sascha@433:
sascha@807: /**
sascha@807: * Default constructor.
sascha@807: */
sascha@431: public XYColumn() {
sascha@433: values = new ArrayList<HeightValue>();
sascha@431: }
ingo@427:
sascha@807: /**
sascha@807: * Constructor to create an XYColumn with a given (x, y) coordinate
sascha@807: * and an (i, j) index tuple.
sascha@807: * @param x The x coordinate.
sascha@807: * @param y The y coordinate.
sascha@807: * @param i The i component.
sascha@807: * @param j The j component.
sascha@807: */
ingo@427: public XYColumn(double x, double y, int i, int j) {
sascha@431: super(x, y, i, j);
sascha@433: values = new ArrayList<HeightValue>();
ingo@427: }
ingo@427:
sascha@807: /**
sascha@807: * Adds a given height value to the list of height values.
sascha@807: * @param value The height value.
sascha@807: */
ingo@427: public void add(HeightValue value) {
ingo@427: values.add(value);
ingo@427: }
ingo@427:
sascha@807: /**
sascha@807: * Returns the list of height values.
sascha@807: * @return The list of height values.
sascha@807: */
sascha@432: public List<HeightValue> getValues() {
sascha@432: return values;
ingo@427: }
sascha@433:
sascha@433: public double value(double depth) {
sascha@433: try {
sascha@433: if (curve != null) {
sascha@434: HeightValue h = values.get(0);
sascha@434: // extrapolate beyond boundaries by repeating
sascha@434: if (depth > h.z) return h.v;
sascha@434: h = values.get(values.size()-1);
sascha@434: if (depth < h.z) return h.v;
sascha@433: return curve.value(depth);
sascha@433: }
sascha@433: }
sascha@433: catch (FunctionEvaluationException fee) {
sascha@433: log.error("evaluation failed", fee);
sascha@433: }
sascha@433:
sascha@433: return Double.NaN;
sascha@433: }
sascha@433:
sascha@807: /**
sascha@807: * Prepares this XYColumn to be queried. A given XYDepth
sascha@807: * object is used to fill the values to a certain depth.
sascha@807: * @param xyDepth To figure out the depth a the cordinate.
sascha@807: * @return true if preparation succeeds else false.
sascha@807: */
sascha@434: public boolean prepare(XYDepth xyDepth) {
sascha@445: if (curve == null) {
sascha@451: int N = values.size();
sascha@445: if (N == 0) {
sascha@445: log.error("no points for interpolation");
sascha@445: return false;
sascha@445: }
sascha@445:
sascha@433: if (N == 1) {
sascha@433: // only one value -> constant function
sascha@433: curve = new ConstantFunction(values.get(0).v);
sascha@433: }
sascha@433: else { // more than on value
sascha@433: double depth = xyDepth.depth(this);
sascha@433: Collections.sort(values, HeightValue.INV_Z_COMPARATOR);
sascha@433:
sascha@433: // if there is no value at 0 repeat first value
sascha@433: HeightValue first = values.get(0);
sascha@433: if (first.z < 0d) {
sascha@448: values.add(0, new HeightValue(0d, first.v, first.k-1));
sascha@445: ++N;
sascha@433: }
sascha@433:
sascha@433: // if there is no value at depth repeat last value
sascha@433: HeightValue last = values.get(N-1);
sascha@433: if (last.z > depth) {
sascha@448: values.add(new HeightValue(depth, last.v, last.k+1));
sascha@445: ++N;
sascha@433: }
sascha@433: if (N < 3) { // interpolate linear
sascha@433: first = values.get(0);
sascha@433: last = values.get(N-1);
sascha@433: curve = new LinearFunction.Univariate(
sascha@433: first.z, first.v,
sascha@433: last.z, last.v);
sascha@433: }
sascha@433: else { // higher degree interpolation
sascha@433: double [] z = new double[N];
sascha@433: double [] v = new double[N];
sascha@433: for (int i = 0; i < N; ++i) {
sascha@445: HeightValue h = values.get(N-1-i);
sascha@433: z[i] = h.z;
sascha@433: v[i] = h.v;
sascha@433: }
sascha@433: try {
sascha@433: curve = getInterpolator().interpolate(z, v);
sascha@433: }
sascha@433: catch (MathException me) {
sascha@433: log.error("interpolation failed", me);
sascha@434: return false;
sascha@433: }
sascha@433: }
sascha@433: }
sascha@433: }
sascha@434: return true;
sascha@433: }
sascha@433:
sascha@807: /**
sascha@807: * Returns the interpolator used to interpolate the values between
sascha@807: * the discrete height values. This class returns an instance of
sascha@807: * {@link org.apache.commons.math.analysis.interpolation.SplineInterpolator}.
sascha@807: * Override this if you want to use another kind of interpolation.
sascha@807: * @return The interpolator to be used.
sascha@807: */
sascha@433: protected UnivariateRealInterpolator getInterpolator() {
sascha@433: return new SplineInterpolator();
sascha@433: }
ingo@427: }
sascha@836: // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :