/*
* Copyright 1998, University Corporation for Atmospheric Research
* All Rights Reserved.
* See file LICENSE for copying and redistribution conditions.
*
* $Id: LonArithProg.java,v 1.3 2001-11-06 17:37:41 steve Exp $
*/
package visad.data.in;
import visad.VisADException;
/**
* Provides support for determining if a sequence of values is an arithmetic
* progression of longitude values and, if so, the progression parameters.
*
* @author Steven R. Emmerson
*/
public final class LonArithProg
extends ArithProg
{
private double sumDel = Double.NaN;
/**
* Accumulates a set of floats. Indicates whether or not the sequence is
* consistent with the arithmetic progression so far.
*
* @param values The values to accumulate.
* @return False if the difference between any current
* and previous value normalized by the current
* increment differs from unity by more than the
* nearness threshold; otherwise, true.
* @throws VisADException {@link #isConsistent()} was false before this
* method was invoked.
* @precondition isConsistent() is true.
* @postcondition A subsequent getNumber() will return
* values.length more than previously
* if the function returns true.
* @postcondition A subsequent getLast() will return the
* value argument if the function returns true.
*/
public synchronized boolean accumulate(float[] values)
throws VisADException
{
if (!isConsistent())
throw new VisADException(
getClass().getName() + ".accumulate(float[]): " +
"Sequence isn't an arithmetic progression");
for (int i = 0; i < values.length; i++)
{
double value = values[i];
if (n == 0)
{
first = value;
}
else if (n == 1)
{
sumDel = meanDel = delta(first, value);
}
else if (isConsistent)
{
accum(value, fEps);
}
last = value;
n++;
}
return isConsistent;
}
/**
* Accumulates a set of doubles. Indicates whether or not the sequence is
* consistent with the arithmetic progression so far.
*
* @param values The values to accumulate.
* @return False if the difference between any current
* and previous value normalized by the current
* increment differs from unity by more than the
* nearness threshold; otherwise, true.
* @throws VisADException {@link #isConsistent()} was false before this
* method was invoked.
* @precondition isConsistent() is true.
* @postcondition A subsequent getNumber() will return
* values.length more than previously
* if the function returns true.
* @postcondition A subsequent getLast() will return the
* value argument if the function returns true.
*/
public synchronized boolean accumulate(double[] values)
throws VisADException
{
if (!isConsistent())
throw new VisADException(
getClass().getName() + ".accumulate(double[]): " +
"Sequence isn't an arithmetic progression");
for (int i = 0; i < values.length; i++)
{
double value = values[i];
if (n == 0)
{
first = value;
}
else if (n == 1)
{
sumDel = meanDel = delta(first, value);
}
else if (isConsistent)
{
accum(value, dEps);
}
last = value;
n++;
}
return isConsistent;
}
private void accum(double value, double eps)
{
double uncLast = last*eps;
double uncValue = value*eps;
double var = uncLast*uncLast + uncValue*uncValue;
double err = delta(last + meanDel, value);
if (err*err > var)
{
isConsistent = false;
}
else
{
sumDel += delta(last, value);
meanDel = sumDel / n;
}
}
/**
* Returns the difference between two values.
*
* @param value1 The first value.
* @param value2 The second value.
* @return The increment from the first value to the
* second value.
*/
private double delta(double value1, double value2)
{
double delta = (value2 - value1) % 360.0;
if (delta < -180.0)
delta += 360.0;
else if (delta > 180.0)
delta -= 360.0;
return delta;
}
/**
* Tests this class.
*
* @param args Runtime arguments. Ignored.
* @throws Exception Something went wrong.
*/
public static void main(String[] args)
throws Exception
{
double[] lons = {
179.2, 179.21, 179.22, 179.23, 179.24, 179.25, 179.26, 179.27, 179.28, 179.29,
179.3, 179.31, 179.32, 179.33, 179.34, 179.35, 179.36, 179.37, 179.38, 179.39,
179.4, 179.41, 179.42, 179.43, 179.44, 179.45, 179.46, 179.47, 179.48, 179.49,
179.5, 179.51, 179.52, 179.53, 179.54, 179.55, 179.56, 179.57, 179.58, 179.59,
179.6, 179.61, 179.62, 179.63, 179.64, 179.65, 179.66, 179.67, 179.68, 179.69,
179.7, 179.71, 179.72, 179.73, 179.74, 179.75, 179.76, 179.77, 179.78, 179.79,
179.8, 179.81, 179.82, 179.83, 179.84, 179.85, 179.86, 179.87, 179.88, 179.89,
179.9, 179.91, 179.92, 179.93, 179.94, 179.95, 179.96, 179.97, 179.98, 179.99,
180,
-179.99, -179.98, -179.97, -179.96, -179.95, -179.94, -179.93, -179.92, -179.91, -179.9,
-179.89, -179.88, -179.87, -179.86, -179.85, -179.84, -179.83, -179.82, -179.81, -179.8,
-179.79, -179.78, -179.77, -179.76, -179.75, -179.74, -179.73, -179.72, -179.71, -179.7,
-179.69, -179.68, -179.67, -179.66, -179.65, -179.64, -179.63, -179.62, -179.61, -179.6,
-179.59, -179.58, -179.57, -179.56, -179.55, -179.54, -179.53, -179.52, -179.51, -179.5,
-179.49, -179.48, -179.47, -179.46, -179.45, -179.44, -179.43, -179.42, -179.41, -179.4,
-179.39, -179.38, -179.37, -179.36, -179.35, -179.34, -179.33, -179.32, -179.31, -179.3,
-179.29, -179.28, -179.27, -179.26, -179.25, -179.24, -179.23, -179.22, -179.21, -179.2};
LonArithProg ap = new LonArithProg();
ap.accumulate(lons);
System.out.println("ap.isConsistent()=" + ap.isConsistent());
System.out.println("ap.getFirst()=" + ap.getFirst());
System.out.println("ap.getLast()=" + ap.getLast());
System.out.println("ap.getNumber()=" + ap.getNumber());
System.out.println("ap.getCommonDifference()=" +
ap.getCommonDifference());
}
}
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