Module org.apache.sis.util
Package org.apache.sis.math

Class Line

Object
Line
All Implemented Interfaces:
Serializable, Cloneable, Double­Unary­Operator
public class Line extends Object implements DoubleUnaryOperator, Cloneable, Serializable
Equation of a line in a two dimensional space (x,y). A line can be expressed by the y = slope⋅x + y₀ equation where y₀ is the value of y at x = 0.

The equation parameters for a Line object can be set at construction time or using one of the set­Line(…) methods. The y value can be computed for a given x value using the y(double) method. Method x(double) computes the converse and should work even if the line is vertical.

Comparison with Java2D geometries

At the difference of Line2D which is bounded by (x₁,y₁) and (x₂,y₂) points, Line objects extend toward infinity.
Since:
0.5
See Also:

  • Constructor Summary

    Constructors
    Constructor
    Description
    Line()
    Constructs an uninitialized line.
    Line(double slope, double y0)
    Constructs a line with the specified slope and offset.

  • Method Summary

    Modifier and Type
    Method
    Description
    double
    apply­As­Double(double x)
    Evaluates this equation for the given value.
    Line
    clone()
    Returns a clone of this line.
    boolean
    equals(Object object)
    Compares this line with the specified object for equality.
    double
    fit(double[] x, double[] y)
    Given a set of data points x[0 … n-1], y[0 … n-1], fits them to a straight line y = slope⋅x + y₀ in a least-squares senses.
    double
    fit(Iterable<? extends Direct­Position> points)
    Given a sequence of points, fits them to a straight line y = slope⋅x + y₀ in a least-squares senses.
    double
    fit(Vector x, Vector y)
    Given a set of data points x[0 … n-1], y[0 … n-1], fits them to a straight line y = slope⋅x + y₀ in a least-squares senses.
    int
    hash­Code()
    Returns a hash code value for this line.
    void
    set­Equation(double slope, double y0)
    Sets this line to the specified slope and offset.
    void
    set­Equation(Number slope, Number y0)
    Sets this line from values of arbitrary Number type.
    void
    set­From­Points(double x1, double y1, double x2, double y2)
    Sets a line through the specified points.
    final double
    slope()
    Returns the slope.
    String
    to­String()
    Returns a string representation of this line.
    void
    translate(double dx, double dy)
    Translates the line.
    final double
    x(double y)
    Computes x = f⁻¹(y).
    final double
    x0()
    Returns the x value for y = 0.
    final double
    y(double x)
    Computes y = f(x).
    final double
    y0()
    Returns the y value for x = 0.

    Methods inherited from class Object

    finalize, get­Class, notify, notify­All, wait, wait, wait

    Methods inherited from interface DoubleUnaryOperator

    and­Then, compose

  • Constructor Details

    • Line

      public Line()
      Constructs an uninitialized line. All methods will return Double​.Na­N.

    • Line

      public Line(double slope, double y0)
      Constructs a line with the specified slope and offset. The linear equation will be y = slope⋅x + y₀.
      Parameters:
      slope - the slope.
      y0 - the y value at x = 0.
      See Also:

  • Method Details

    • slope

      public final double slope()
      Returns the slope.
      Returns:
      the slope.
      See Also:

    • x0

      public final double x0()
      Returns the x value for y = 0. Coordinate (x₀, 0) is the intersection point with the x axis.
      Returns:
      the x value for y = 0.
      See Also:

    • x

      public final double x(double y)
      Computes x = f⁻¹(y). If the line is horizontal, then this method returns an infinite value.
      Parameters:
      y - the y value where to evaluate the inverse function.
      Returns:
      the x value for the given y value.
      See Also:

    • y0

      public final double y0()
      Returns the y value for x = 0. Coordinate (0, y₀) is the intersection point with the y axis.
      Returns:
      the y value for x = 0.
      See Also:

    • y

      public final double y(double x)
      Computes y = f(x). If the line is vertical, then this method returns an infinite value.
      Parameters:
      x - the x value where to evaluate the function.
      Returns:
      the y value for the given x value.
      See Also:

    • applyAsDouble

      public double applyAsDouble(double x)
      Evaluates this equation for the given value. The default implementation delegates to y(x), but subclasses may override with different formulas. This method is provided for interoperability with libraries making use of java​.util​.function.
      Specified by:
      apply­As­Double in interface Double­Unary­Operator
      Parameters:
      x - the value where to evaluate the function.
      Returns:
      the function value for the given operand.
      Since:
      1.0

    • translate

      public void translate(double dx, double dy)
      Translates the line. The slope stay unchanged.
      Parameters:
      dx - the horizontal translation.
      dy - the vertical translation.

    • setEquation

      public void setEquation(double slope, double y0)
      Sets this line to the specified slope and offset. The linear equation will be y = slope⋅x + y₀.
      Parameters:
      slope - the slope.
      y0 - the y value at x = 0.
      See Also:

    • setEquation

      public void setEquation(Number slope, Number y0)
      Sets this line from values of arbitrary Number type. This method is invoked by algorithms that may produce other kind of numbers (for example with different precision) than the usual double primitive type. The default implementation delegates to set­Equation(double, double), but subclasses can override this method if they want to process other kind of numbers in a special way.
      Parameters:
      slope - the slope.
      y0 - the y value at x = 0.
      Since:
      0.8

    • setFromPoints

      public void setFromPoints(double x1, double y1, double x2, double y2)
      Sets a line through the specified points. The line will continue toward infinity after the points.
      Parameters:
      x1 - coordinate x of the first point.
      y1 - coordinate y of the first point.
      x2 - coordinate x of the second point.
      y2 - coordinate y of the second point.

    • fit

      public double fit(double[] x, double[] y)
      Given a set of data points x[0 … n-1], y[0 … n-1], fits them to a straight line y = slope⋅x + y₀ in a least-squares senses. This method assumes that the x values are precise and all uncertainty is in y.

      The default implementation delegates to fit(Vector, Vector).

      Parameters:
      x - vector of x values (independent variable).
      y - vector of y values (dependent variable).
      Returns:
      estimation of the correlation coefficient. The closer this coefficient is to +1 or -1, the better the fit.
      Throws:
      Illegal­Argument­Exception - if x and y do not have the same length.

    • fit

      public double fit(Vector x, Vector y)
      Given a set of data points x[0 … n-1], y[0 … n-1], fits them to a straight line y = slope⋅x + y₀ in a least-squares senses. This method assumes that the x values are precise and all uncertainty is in y.

      The default implementation delegates to fit(Iterable).

      Parameters:
      x - vector of x values (independent variable).
      y - vector of y values (dependent variable).
      Returns:
      estimation of the correlation coefficient. The closer this coefficient is to +1 or -1, the better the fit.
      Throws:
      Illegal­Argument­Exception - if x and y do not have the same length.
      Since:
      0.8

    • fit

      public double fit(Iterable<? extends DirectPosition> points)
      Given a sequence of points, fits them to a straight line y = slope⋅x + y₀ in a least-squares senses. Points shall be two dimensional with coordinate values in the (x,y) order. This method assumes that the x values are precise and all uncertainty is in y. Double​.Na­N coordinate values are ignored.
      Parameters:
      points - the two-dimensional points.
      Returns:
      estimation of the correlation coefficient. The closer this coefficient is to +1 or -1, the better the fit.
      Throws:
      Mismatched­Dimension­Exception - if a point is not two-dimensional.

    • clone

      public Line clone()
      Returns a clone of this line.
      Overrides:
      clone in class Object
      Returns:
      a clone of this line.

    • equals

      public boolean equals(Object object)
      Compares this line with the specified object for equality.
      Overrides:
      equals in class Object
      Parameters:
      object - the object to compare with this line for equality.
      Returns:
      true if both objects are equal.

    • hashCode

      public int hashCode()
      Returns a hash code value for this line.
      Overrides:
      hash­Code in class Object

    • toString

      public String toString()
      Returns a string representation of this line. This method returns the linear equation in the form y = slope⋅x + y₀.
      Overrides:
      to­String in class Object
      Returns:
      a string representation of this line.