Class Shapes

java.lang.Object
uk.ac.starlink.ttools.func.Shapes

public class Shapes extends Object
Functions useful for working with shapes in the (X, Y) plane.
Since:
18 Sep 2018
Author:
Mark Taylor
  • Method Summary

    Modifier and Type
    Method
    Description
    static boolean
    isInside(double x, double y, double... xys)
    Indicates whether a given test point is inside a polygon defined by specified list of vertices.
    static double
    polyLine(double x, double... xys)
    Function of x defined by straight line segments between a specified list of vertices.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  • Method Details

    • polyLine

      public static double polyLine(double x, double... xys)
      Function of x defined by straight line segments between a specified list of vertices. The vertices are specified as a sequence of Xi, Yi pairs, for which the Xi values must be monotonic. The line segment at each end of the specified point sequence is considered to be extended to infinity. If only two points are specified, this is the equation of a straight line between those points. As a special case, if only one point is specified, the line is considered to be a horizontal line (equal to the sole specified Yi coordinate for all x).

      By reversing the Xi and Yi values, this function can equally be used to represent a function X(y) rather than Y(x).

      If the number of coordinates is odd, or the Xi values are not monotonic, behaviour is undefined.

      Parameters:
      x - X value at which function is to be evaluated
      xys - 2N arguments (x1, y1, x2, y2, ..., xN, yN) giving vertices of an N-point line with monotonically increasing or decreasing X values
      Returns:
      Y coordinate of poly-line for specified x
      Examples:
      polyLine(5, 0,0, 2,2) = 5
    • isInside

      public static boolean isInside(double x, double y, double... xys)
      Indicates whether a given test point is inside a polygon defined by specified list of vertices. The vertices are specified as a sequence of Xi, Yi pairs.

      If the number of coordinates is odd, the behaviour is not defined.

      Parameters:
      x - X coordinate of test point
      y - Y coordinate of test point
      xys - 2N arguments (x1, y1, x2, y2, ..., xN, yN) giving vertices of an N-sided polygon
      Returns:
      true iff test point is inside, or on the border of, the polygon
      Examples:
      isInside(0.5,0.5, 0,0, 0,1, 1,1, 1,0) = true, isInside(0,0, array(10,20, 20,20, 20,10)) = false