Package uk.ac.starlink.ttools.func
Class Shapes
java.lang.Object
uk.ac.starlink.ttools.func.Shapes
Functions useful for working with shapes in the (X, Y) plane.
- Since:
- 18 Sep 2018
- Author:
- Mark Taylor
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Method Summary
Modifier and TypeMethodDescriptionstatic 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 ofx
defined by straight line segments between a specified list of vertices.
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Method Details
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polyLine
public static double polyLine(double x, double... xys) Function ofx
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 allx
).By reversing the Xi and Yi values, this function can equally be used to represent a function
X(y)
rather thanY(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 evaluatedxys
- 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
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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 pointy
- Y coordinate of test pointxys
- 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
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