//******************************************************************************
//
// File: XYSeries.java
// Package: edu.rit.numeric
// Unit: Class edu.rit.numeric.XYSeries
//
// This Java source file is copyright (C) 2011 by Alan Kaminsky. All rights
// reserved. For further information, contact the author, Alan Kaminsky, at
// ark@cs.rit.edu.
//
// This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
// software; you can redistribute it and/or modify it under the terms of the GNU
// General Public License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// PJ is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
//
// A copy of the GNU General Public License is provided in the file gpl.txt. You
// may also obtain a copy of the GNU General Public License on the World Wide
// Web at http://www.gnu.org/licenses/gpl.html.
//
//******************************************************************************
package edu.rit.numeric;
import java.io.PrintStream;
import java.io.PrintWriter;
/**
* Class XYSeries is the abstract base class for a series of (x,y) pairs
* of real values (type double).
*
* @author Alan Kaminsky
* @version 20-Jul-2011
*/
public abstract class XYSeries
{
// Exported helper classes.
/**
* Class XYSeries.Regression holds the results of a regression on an
* {@linkplain XYSeries}.
*
* @author Alan Kaminsky
* @version 12-Jun-2007
*/
public static class Regression
{
/**
* Intercept a.
*/
public final double a;
/**
* Slope b.
*/
public final double b;
/**
* Correlation.
*/
public final double corr;
/**
* Construct a new Regression object.
*/
private Regression
(double a,
double b,
double corr)
{
this.a = a;
this.b = b;
this.corr = corr;
}
}
/**
* Class XYSeries.XSeriesView provides a series view of the X values in an
* XY series.
*
* @author Alan Kaminsky
* @version 12-Jun-2007
*/
private static class XSeriesView
extends Series
{
private XYSeries outer;
public XSeriesView
(XYSeries outer)
{
this.outer = outer;
}
public int length()
{
return outer.length();
}
public double x
(int i)
{
return outer.x (i);
}
}
/**
* Class XYSeries.YSeriesView provides a series view of the Y values in an
* XY series.
*
* @author Alan Kaminsky
* @version 12-Jun-2007
*/
private static class YSeriesView
extends Series
{
private XYSeries outer;
public YSeriesView
(XYSeries outer)
{
this.outer = outer;
}
public int length()
{
return outer.length();
}
public double x
(int i)
{
return outer.y (i);
}
}
// Exported constructors.
/**
* Construct a new XY series.
*/
public XYSeries()
{
}
// Exported operations.
/**
* Returns the number of values in this series.
*
* @return Length.
*/
public abstract int length();
/**
* Determine if this series is empty.
*
* @return True if this series is empty (length = 0), false otherwise.
*/
public boolean isEmpty()
{
return length() == 0;
}
/**
* Returns the given X value in this series.
*
* @param i Index.
*
* @return The X value in this series at index i.
*
* @exception ArrayIndexOutOfBoundsException
* (unchecked exception) Thrown if i is not in the range
* 0 .. length()-1.
*/
public abstract double x
(int i);
/**
* Returns the given Y value in this series.
*
* @param i Index.
*
* @return The Y value in this series at index i.
*
* @exception ArrayIndexOutOfBoundsException
* (unchecked exception) Thrown if i is not in the range
* 0 .. length()-1.
*/
public abstract double y
(int i);
/**
* Returns the minimum X value in this series.
*
* @return Minimum X value.
*/
public double minX()
{
int n = length();
double result = Double.POSITIVE_INFINITY;
for (int i = 0; i < n; ++ i) result = Math.min (result, x(i));
return result;
}
/**
* Returns the maximum X value in this series.
*
* @return Maximum X value.
*/
public double maxX()
{
int n = length();
double result = Double.NEGATIVE_INFINITY;
for (int i = 0; i < n; ++ i) result = Math.max (result, x(i));
return result;
}
/**
* Returns the minimum Y value in this series.
*
* @return Minimum Y value.
*/
public double minY()
{
int n = length();
double result = Double.POSITIVE_INFINITY;
for (int i = 0; i < n; ++ i) result = Math.min (result, y(i));
return result;
}
/**
* Returns the maximum Y value in this series.
*
* @return Maximum Y value.
*/
public double maxY()
{
int n = length();
double result = Double.NEGATIVE_INFINITY;
for (int i = 0; i < n; ++ i) result = Math.max (result, y(i));
return result;
}
/**
* Returns the linear regression of the (x,y) values in this XY
* series. The linear function y = a + bx is fitted to
* the data. The return value is a {@linkplain Regression Regression} object
* containing the intercept a, the slope b, and the
* correlation, respectively.
*
* Note: The returned object contains the regression of a
* snapshot of this series at the time linearRegression()
* was called. Changing the data in this series will not change the
* contents of the returned object.
*
* @return Regression.
*/
public Regression linearRegression()
{
// Accumulate sums.
int n = length();
double sum_x = 0.0;
double sum_y = 0.0;
for (int i = 0; i < n; ++ i)
{
sum_x += x(i);
sum_y += y(i);
}
// Compute means of X and Y.
double mean_x = sum_x / n;
double mean_y = sum_y / n;
// Compute variances of X and Y.
double xt;
double yt;
double sum_xt_sqr = 0.0;
double sum_yt_sqr = 0.0;
double sum_xt_yt = 0.0;
double b = 0.0;
for (int i = 0; i < n; ++ i)
{
xt = x(i) - mean_x;
yt = y(i) - mean_y;
sum_xt_sqr += xt * xt;
sum_yt_sqr += yt * yt;
sum_xt_yt += xt * yt;
b += xt * y(i);
}
// Compute results.
b /= sum_xt_sqr;
double a = (sum_y - sum_x * b) / n;
double corr = sum_xt_yt / (Math.sqrt (sum_xt_sqr * sum_yt_sqr) + TINY);
return new Regression (a, b, corr);
}
private static final double TINY = 1.0e-20;
/**
* Returns a {@linkplain Series} view of the X values in this XY series.
*
* Note: The returned Series object is backed by this XY series
* object. Changing the contents of this XY series object will change the
* contents of the returned Series object.
*
* @return Series of X values.
*/
public Series xSeries()
{
return new XSeriesView (this);
}
/**
* Returns a {@linkplain Series} view of the Y values in this XY series.
*
* Note: The returned Series object is backed by this XY series
* object. Changing the contents of this XY series object will change the
* contents of the returned Series object.
*
* @return Series of Y values.
*/
public Series ySeries()
{
return new YSeriesView (this);
}
/**
* Print this XY series on the standard output. Each line of output consists
* of the index, the x value, and the y value, separated by
* tabs.
*/
public void print()
{
print (System.out);
}
/**
* Print this XY series on the given print stream. Each line of output
* consists of the index, the x value, and the y value,
* separated by tabs.
*
* @param theStream Print stream.
*/
public void print
(PrintStream theStream)
{
int n = length();
for (int i = 0; i < n; ++ i)
{
theStream.print (i);
theStream.print ('\t');
theStream.print (x(i));
theStream.print ('\t');
theStream.println (y(i));
}
}
/**
* Print this XY series on the given print writer. Each line of output
* consists of the index, the x value, and the y value,
* separated by tabs.
*
* @param theWriter Print writer.
*/
public void print
(PrintWriter theWriter)
{
int n = length();
for (int i = 0; i < n; ++ i)
{
theWriter.print (i);
theWriter.print ('\t');
theWriter.print (x(i));
theWriter.print ('\t');
theWriter.println (y(i));
}
}
}
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