uk.ac.starlink.ttools.func

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 and 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 Detail

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 X_i, Y_i pairs, for which the X_i 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 Y_i coordinate for all x).

By reversing the X_i and Y_i 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 X_i 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

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 X_i, Y_i 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