package org.spaceroots.mantissa.estimation;

import java.io.Serializable;

/** This class represents measurements in estimation problems.

 * 
This abstract class implements all the methods needed to handle
 * measurements in a general way. It defines neither the {@link
 * #getTheoreticalValue getTheoreticalValue} nor the {@link
 * #getPartial getPartial} methods, which should be defined by
 * sub-classes according to the specific problem.

 * 
The {@link #getTheoreticalValue getTheoreticalValue} and {@link
 * #getPartial getPartial} methods must always use the current
 * estimate of the parameters set by the solver in the problem. These
 * parameters can be retrieved through the {@link
 * EstimationProblem#getAllParameters
 * EstimationProblem.getAllParameters} method if the measurements are
 * independant of the problem, or directly if they are implemented as
 * inner classes of the problem.

 * 
The instances for which the ignored flag is set
 * through the {@link #setIgnored setIgnored} method are ignored by the
 * solvers. This can be used to reject wrong measurements at some
 * steps of the estimation.

 * @see EstimationProblem

 * @version $Id: WeightedMeasurement.java 1679 2005-12-16 11:12:23Z luc $
 * @author L. Maisonobe

 */

public abstract class WeightedMeasurement implements Serializable {

  /** Simple constructor.
   * Build a measurement with the given parameters, and set its ignore
   * flag to false.
   * @param weight weight of the measurement in the least squares problem
   * (two common choices are either to use 1.0 for all measurements, or to
   * use a value proportional to the inverse of the variance of the measurement
   * type)
   * @param measuredValue measured value
   */
  public WeightedMeasurement(double weight, double measuredValue) {
    this.weight        = weight;
    this.measuredValue = measuredValue;
    ignored            = false;
  }

  /** Simple constructor.
   * Build a measurement with the given parameters
   * @param weight weight of the measurement in the least squares problem
   * @param measuredValue measured value
   * @param ignored true if the measurement should be ignored
   */
  public WeightedMeasurement(double weight, double measuredValue,
                             boolean ignored) {
    this.weight        = weight;
    this.measuredValue = measuredValue;
    this.ignored       = ignored;
  }

  /** Get the weight of the measurement in the least squares problem
   * @return weight
   */
  public double getWeight() {
    return weight;
  }

  /** Get the measured value
   * @return measured value
   */
  public double getMeasuredValue() {
    return measuredValue;
  }

  /** Get the residual for this measurement
   * The residual is the measured value minus the theoretical value.
   * @return residual
   */
  public double getResidual() {
    return measuredValue - getTheoreticalValue();
  }

  /** Get the theoretical value expected for this measurement
   * 
The theoretical value is the value expected for this measurement
   * if the model and its parameter were all perfectly known.
   * 
The value must be computed using the current estimate of the parameters
   * set by the solver in the problem.
   * @return theoretical value
   */
  public abstract double getTheoreticalValue();

  /** Get the partial derivative of the {@link #getTheoreticalValue
   * theoretical value} according to the parameter.
   * 
The value must be computed using the current estimate of the parameters
   * set by the solver in the problem.
   * @param parameter parameter against which the partial derivative
   * should be computed
   * @return partial derivative of the {@link #getTheoreticalValue
   * theoretical value}
   */
  public abstract double getPartial(EstimatedParameter parameter);

  /** Set the ignore flag to the specified value
   * Setting the ignore flag to true allow to reject wrong
   * measurements, which sometimes can be detected only rather late.
   * @param ignored value for the ignore flag
   */
  public void setIgnored(boolean ignored) {
    this.ignored = ignored;
  }

  /** Check if this measurement should be ignored
   * @return true if the measurement should be ignored
   */
  public boolean isIgnored() {
    return ignored;
  }

  private final double  weight;
  private final double  measuredValue;
  private       boolean ignored;

}