sascha@361: package de.intevation.gnv.math;
sascha@361:
sascha@593: import com.vividsolutions.jts.geom.Coordinate;
sascha@593: import com.vividsolutions.jts.geom.Envelope;
sascha@593:
sascha@361: import java.util.Comparator;
sascha@361:
sascha@593: import org.apache.log4j.Logger;
sascha@361:
sascha@361: /**
sascha@798: * Point which besides the x, y, z coodinates has an index i, j pair
sascha@798: * to model neighborhood.
sascha@798: * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a>
sascha@361: */
sascha@361: public class Point2d
sascha@361: extends Coordinate
sascha@361: {
sascha@593: private static Logger log = Logger.getLogger(Point2d.class);
sascha@593:
sascha@798: /**
sascha@798: * Numerical tolerance epsilon: {@value}
sascha@798: */
ingo@365: public static final double EPSILON = 1e-3d;
sascha@361:
sascha@798: /**
sascha@798: * Compares two Point2ds by their x coordinates
sascha@798: */
sascha@361: public static final Comparator X_COMPARATOR = new Comparator() {
sascha@361: public int compare(Object a, Object b) {
sascha@361: double xa = ((Coordinate)a).x;
sascha@361: double xb = ((Coordinate)b).x;
sascha@361: if (xa < xb) return -1;
sascha@361: if (xa > xb) return +1;
sascha@361: return 0;
sascha@361: }
sascha@361: };
sascha@361:
sascha@798: /**
sascha@798: * Compares two Point2ds by their y coordinates.
sascha@798: */
sascha@361: public static final Comparator Y_COMPARATOR = new Comparator() {
sascha@361: public int compare(Object a, Object b) {
sascha@361: double ya = ((Coordinate)a).y;
sascha@361: double yb = ((Coordinate)b).y;
sascha@361: if (ya < yb) return -1;
sascha@361: if (ya > yb) return +1;
sascha@361: return 0;
sascha@361: }
sascha@361: };
sascha@361:
sascha@798: /**
sascha@798: * The i index of this Point2d.
sascha@798: */
sascha@361: public int i;
sascha@798: /**
sascha@798: * The j index of this Point2d.
sascha@798: */
sascha@361: public int j;
sascha@361:
sascha@798: /**
sascha@798: * Default constructor.
sascha@798: */
sascha@361: public Point2d() {
sascha@361: }
sascha@361:
sascha@798: /**
sascha@798: * Constructor setting x and y coordinate.
sascha@798: * @param x The x coordinate.
sascha@798: * @param y The y coordinate.
sascha@798: */
sascha@593: public Point2d(double x, double y) {
sascha@593: super(x, y);
sascha@593: }
sascha@593:
sascha@798: /**
sascha@798: * Constructor setting x, y and i, j.
sascha@798: * @param x The x coordinate.
sascha@798: * @param y The y coordinate.
sascha@798: * @param i The i index.
sascha@798: * @param j The j index.
sascha@798: */
sascha@431: public Point2d(double x, double y, int i, int j) {
sascha@431: super(x, y);
sascha@431: this.i = i;
sascha@431: this.j = j;
sascha@431: }
sascha@431:
sascha@798: /**
sascha@798: * Constructor setting x, y, z and i, j.
sascha@798: * @param x The x coordinate.
sascha@798: * @param y The y coordinate.
sascha@798: * @param z The z coordinate.
sascha@798: * @param i The i index.
sascha@798: * @param j The j index.
sascha@798: */
sascha@361: public Point2d(double x, double y, double z, int i, int j) {
sascha@361: super(x, y, z);
sascha@361: this.i = i;
sascha@361: this.j = j;
sascha@361: }
sascha@361:
sascha@798: /**
sascha@798: * Calculates the L1 distance to another Point2d.
sascha@798: * @param other The other Point2d.
sascha@798: * @return The L1 distance.
sascha@798: */
sascha@361: public double L1(Point2d other) {
sascha@798: return L1Comparator.L1(this, other);
sascha@361: }
sascha@361:
sascha@798: /**
sascha@798: * Creates an envelope around this Point2d with
sascha@798: * the numerical tolerance of {@link #EPSILON}.
sascha@798: * @return The envelope.
sascha@798: */
sascha@361: public Envelope envelope() {
sascha@361: return envelope(EPSILON);
sascha@361: }
sascha@361:
sascha@798: /**
sascha@798: *Creates an envelope around this Point2d with
sascha@798: * a given tolerance.
sascha@798: * @param epsilon The tolerance in all directions.
sascha@798: * @return The envelope.
sascha@798: */
sascha@361: public Envelope envelope(double epsilon) {
sascha@361: return new Envelope(
sascha@361: x-epsilon, x+epsilon,
sascha@361: y-epsilon, y+epsilon);
sascha@361: }
sascha@361:
sascha@798: /**
sascha@798: * Given this and another Point2d it looks if there is
sascha@798: * a gap between the in points in i index direction.
sascha@798: * @param other The other Point2d.
sascha@798: * @return true if there is is a gap, else false.
sascha@798: */
sascha@361: public boolean hasIGap(Point2d other) {
sascha@361: return Math.abs(i - other.i) > 1;
sascha@361: }
sascha@361:
sascha@798: /**
sascha@798: * Given this and another Point2d it looks if there is
sascha@798: * a gap between the in points in j index direction.
sascha@798: * @param other The other Point2d.
sascha@798: * @return true if there is is a gap, else false.
sascha@798: */
sascha@361: public boolean hasJGap(Point2d other) {
sascha@361: return Math.abs(j - other.j) > 1;
sascha@361: }
sascha@593:
sascha@798: /**
sascha@798: * Given this and another Point2d a new Point2d is
sascha@798: * created via {@link #newPoint() }. The x, y coordinate
sascha@798: * of the new point is on the line of this and the other
sascha@798: * given point at a given scaling point.
sascha@798: * @param t The scaling factor.
sascha@798: * @param other The other point.
sascha@798: * @return The new Point2d.
sascha@798: */
sascha@593: public Point2d extrapolate(double t, Point2d other) {
sascha@593: if (other == null) {
sascha@593: return null;
sascha@593: }
sascha@593: Point2d p = newPoint();
sascha@593: p.x = t*(other.x - x) + x;
sascha@593: p.y = t*(other.y - y) + y;
sascha@593: return p;
sascha@593: }
sascha@593:
sascha@798: /**
sascha@798: * Creates a new Point2d or an instance of a subclass.
sascha@798: * Override this in subclasses.
sascha@798: * @return The new Point2d.
sascha@798: */
sascha@593: public Point2d newPoint() {
sascha@593: return new Point2d(0d, 0d);
sascha@593: }
sascha@593:
sascha@798: /**
sascha@798: * Creates a new Point2d or an instance of a subclass
sascha@798: * at a given coordinate.
sascha@798: * Override this in subclasses.
sascha@798: * @param x The x coordinate.
sascha@798: * @param y The y coordinate.
sascha@798: * @return The new point.
sascha@798: */
sascha@593: public Point2d newPoint(double x, double y) {
sascha@593: return new Point2d(x, y);
sascha@593: }
sascha@593:
sascha@798: /**
sascha@798: * Sets the z value to the inverse distance weighting (IDW) value
sascha@798: * of the z values of a set of given points.
sascha@798: * @param ps The points from wich the z values are taken
sascha@798: * to calculate the IDW.
sascha@798: */
sascha@593: public void inverseDistanceWeighting(Point2d [] ps) {
sascha@593:
sascha@593: double sum = 0d;
sascha@593:
sascha@593: double [] d = new double[ps.length];
sascha@593:
sascha@593: for (int i = 0; i < ps.length; ++i) {
sascha@593: Point2d p = ps[i];
sascha@593: if (p != null) {
sascha@593: double di = distance(p);
sascha@593: if (di < 1e-5d) { z = p.z; return; }
sascha@593: di = 1d/di;
sascha@593: d[i] = di;
sascha@593: sum += di;
sascha@593: }
sascha@593: }
sascha@593:
sascha@593: if (sum == 0d) {
sascha@593: return;
sascha@593: }
sascha@593:
sascha@593: double v = 0d;
sascha@593:
sascha@593: for (int i = 0; i < ps.length; ++i) {
sascha@593: Point2d p = ps[i];
sascha@593: if (p != null) {
sascha@593: v += p.z*d[i];
sascha@593: }
sascha@593: }
sascha@593: z = v/sum;
sascha@593: }
sascha@593:
sascha@798: /**
sascha@798: * Creates a new point via {@link #newPoint() } with the
sascha@798: * x,y coordinates of the center of a given set of
sascha@798: * coordinates.
sascha@798: * @param ps The points from which the x,y coordinates are
sascha@798: * taken to calculate the center.
sascha@798: * @return The new center point.
sascha@798: */
sascha@593: public static Point2d average(Point2d [] ps) {
sascha@593:
sascha@593: Point2d p = null;
sascha@593: int count = 0;
sascha@593:
sascha@593: for (int i = 0; i < ps.length; ++i) {
sascha@593: Point2d t = ps[i];
sascha@593: if (t != null) {
sascha@593: ++count;
sascha@593: if (p == null) {
sascha@593: p = t.newPoint(t.x, t.y);
sascha@593: }
sascha@593: else {
sascha@593: p.x += t.x;
sascha@593: p.y += t.y;
sascha@593: }
sascha@593: }
sascha@593: }
sascha@593:
sascha@593: if (p != null) {
sascha@593: double s = 1d/count;
sascha@593: p.x *= s;
sascha@593: p.y *= s;
sascha@593: }
sascha@593:
sascha@593: return p;
sascha@593: }
sascha@593:
sascha@798: /**
sascha@798: * Checks if this Point2d is near to at least one point
sascha@798: * out of a given set of points. Near is defined by an
sascha@798: * euclidian distance small than {@link #EPSILON}.
sascha@798: * @param ps The set of points to be tested.
sascha@798: * @return true if this Point2d is near to one of the given
sascha@798: * points, else false.
sascha@798: */
sascha@593: public boolean near(Point2d [] ps) {
sascha@593:
sascha@593: for (int i = 0; i < ps.length; ++i) {
sascha@593: Point2d p = ps[i];
sascha@593: if (p != null && distance(p) > EPSILON) {
sascha@593: return false;
sascha@593: }
sascha@593: }
sascha@593:
sascha@593: return true;
sascha@593: }
sascha@361: }
sascha@798: // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :