org.apache.commons.math3.ode

## Class ContinuousOutputModel

- java.lang.Object
- - org.apache.commons.math3.ode.ContinuousOutputModel

- All Implemented Interfaces:
    Serializable, StepHandler

      public class ContinuousOutputModel
      extends Object
      implements StepHandler, Serializable

  This class stores all information provided by an ODE integrator during the integration process and build a continuous model of the solution from this.

  This class act as a step handler from the integrator point of view. It is called iteratively during the integration process and stores a copy of all steps information in a sorted collection for later use. Once the integration process is over, the user can use the `setInterpolatedTime` and `getInterpolatedState` to retrieve this information at any time. It is important to wait for the integration to be over before attempting to call `setInterpolatedTime` because some internal variables are set only once the last step has been handled.

  This is useful for example if the main loop of the user application should remain independent from the integration process or if one needs to mimic the behaviour of an analytical model despite a numerical model is used (i.e. one needs the ability to get the model value at any time or to navigate through the data).

  If problem modeling is done with several separate integration phases for contiguous intervals, the same ContinuousOutputModel can be used as step handler for all integration phases as long as they are performed in order and in the same direction. As an example, one can extrapolate the trajectory of a satellite with one model (i.e. one set of differential equations) up to the beginning of a maneuver, use another more complex model including thrusters modeling and accurate attitude control during the maneuver, and revert to the first model after the end of the maneuver. If the same continuous output model handles the steps of all integration phases, the user do not need to bother when the maneuver begins or ends, he has all the data available in a transparent manner.

  An important feature of this class is that it implements the `Serializable` interface. This means that the result of an integration can be serialized and reused later (if stored into a persistent medium like a filesystem or a database) or elsewhere (if sent to another application). Only the result of the integration is stored, there is no reference to the integrated problem by itself.

  One should be aware that the amount of data stored in a ContinuousOutputModel instance can be important if the state vector is large, if the integration interval is long or if the steps are small (which can result from small tolerance settings in `adaptive step size integrators`).

  Since:
    1.2
  See Also:
    `StepHandler`, `StepInterpolator`, Serialized Form

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `ContinuousOutputModel()` Simple constructor.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `append(ContinuousOutputModel model)` Append another model at the end of the instance.
    `double` | `getFinalTime()` Get the final integration time.
    `double` | `getInitialTime()` Get the initial integration time.
    `double[]` | `getInterpolatedDerivatives()` Get the derivatives of the state vector of the interpolated point.
    `double[]` | `getInterpolatedSecondaryDerivatives(int secondaryStateIndex)` Get the interpolated secondary derivatives corresponding to the secondary equations.
    `double[]` | `getInterpolatedSecondaryState(int secondaryStateIndex)` Get the interpolated secondary state corresponding to the secondary equations.
    `double[]` | `getInterpolatedState()` Get the state vector of the interpolated point.
    `double` | `getInterpolatedTime()` Get the time of the interpolated point.
    `void` | `handleStep(StepInterpolator interpolator, boolean isLast)` Handle the last accepted step.
    `void` | `init(double t0, double[] y0, double t)` Initialize step handler at the start of an ODE integration.
    `void` | `setInterpolatedTime(double time)` Set the time of the interpolated point.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### ContinuousOutputModel

          public ContinuousOutputModel()

      Simple constructor. Build an empty continuous output model.

  - ### Method Detail

    - #### append

          public void append(ContinuousOutputModel model)
                      throws MathIllegalArgumentException,
                             MaxCountExceededException

      Append another model at the end of the instance.
      Parameters:
        `model` - model to add at the end of the instance
      Throws:
        `MathIllegalArgumentException` - if the model to append is not compatible with the instance (dimension of the state vector, propagation direction, hole between the dates)
        `MaxCountExceededException` - if the number of functions evaluations is exceeded during step finalization

    - #### init

          public void init(double t0,
                  double[] y0,
                  double t)

      Initialize step handler at the start of an ODE integration.

      This method is called once at the start of the integration. It may be used by the step handler to initialize some internal data if needed.

      Specified by:
        `init` in interface `StepHandler`
      Parameters:
        `t0` - start value of the independent time variable
        `y0` - array containing the start value of the state vector
        `t` - target time for the integration

    - #### handleStep

          public void handleStep(StepInterpolator interpolator,
                        boolean isLast)
                          throws MaxCountExceededException

      Handle the last accepted step. A copy of the information provided by the last step is stored in the instance for later use.
      Specified by:
        `handleStep` in interface `StepHandler`
      Parameters:
        `interpolator` - interpolator for the last accepted step.
        `isLast` - true if the step is the last one
      Throws:
        `MaxCountExceededException` - if the number of functions evaluations is exceeded during step finalization

    - #### getInitialTime

          public double getInitialTime()

      Get the initial integration time.
      Returns:
        initial integration time

    - #### getFinalTime

          public double getFinalTime()

      Get the final integration time.
      Returns:
        final integration time

    - #### getInterpolatedTime

          public double getInterpolatedTime()

      Get the time of the interpolated point. If `setInterpolatedTime(double)` has not been called, it returns the final integration time.
      Returns:
        interpolation point time

    - #### setInterpolatedTime

          public void setInterpolatedTime(double time)

      Set the time of the interpolated point.

      This method should not be called before the integration is over because some internal variables are set only once the last step has been handled.

      Setting the time outside of the integration interval is now allowed, but should be used with care since the accuracy of the interpolator will probably be very poor far from this interval. This allowance has been added to simplify implementation of search algorithms near the interval endpoints.

      Note that each time this method is called, the internal arrays returned in `getInterpolatedState()`, `getInterpolatedDerivatives()` and `getInterpolatedSecondaryState(int)` will be overwritten. So if their content must be preserved across several calls, user must copy them.

      Parameters:
        `time` - time of the interpolated point
      See Also:
        `getInterpolatedState()`, `getInterpolatedDerivatives()`, `getInterpolatedSecondaryState(int)`

    - #### getInterpolatedState

          public double[] getInterpolatedState()
                                        throws MaxCountExceededException

      Get the state vector of the interpolated point.

      The returned vector is a reference to a reused array, so it should not be modified and it should be copied if it needs to be preserved across several calls to the associated `setInterpolatedTime(double)` method.

      Returns:
        state vector at time `getInterpolatedTime()`
      Throws:
        `MaxCountExceededException` - if the number of functions evaluations is exceeded
      See Also:
        `setInterpolatedTime(double)`, `getInterpolatedDerivatives()`, `getInterpolatedSecondaryState(int)`, `getInterpolatedSecondaryDerivatives(int)`

    - #### getInterpolatedDerivatives

          public double[] getInterpolatedDerivatives()
                                              throws MaxCountExceededException

      Get the derivatives of the state vector of the interpolated point.

      The returned vector is a reference to a reused array, so it should not be modified and it should be copied if it needs to be preserved across several calls to the associated `setInterpolatedTime(double)` method.

      Returns:
        derivatives of the state vector at time `getInterpolatedTime()`
      Throws:
        `MaxCountExceededException` - if the number of functions evaluations is exceeded
      Since:
        3.4
      See Also:
        `setInterpolatedTime(double)`, `getInterpolatedState()`, `getInterpolatedSecondaryState(int)`, `getInterpolatedSecondaryDerivatives(int)`

    - #### getInterpolatedSecondaryState

          public double[] getInterpolatedSecondaryState(int secondaryStateIndex)
                                                 throws MaxCountExceededException

      Get the interpolated secondary state corresponding to the secondary equations.

      The returned vector is a reference to a reused array, so it should not be modified and it should be copied if it needs to be preserved across several calls to the associated `setInterpolatedTime(double)` method.

      Parameters:
        `secondaryStateIndex` - index of the secondary set, as returned by `ExpandableStatefulODE.addSecondaryEquations(SecondaryEquations)`
      Returns:
        interpolated secondary state at the current interpolation date
      Throws:
        `MaxCountExceededException` - if the number of functions evaluations is exceeded
      Since:
        3.2
      See Also:
        `setInterpolatedTime(double)`, `getInterpolatedState()`, `getInterpolatedDerivatives()`, `getInterpolatedSecondaryDerivatives(int)`

    - #### getInterpolatedSecondaryDerivatives

          public double[] getInterpolatedSecondaryDerivatives(int secondaryStateIndex)
                                                       throws MaxCountExceededException

      Get the interpolated secondary derivatives corresponding to the secondary equations.

      The returned vector is a reference to a reused array, so it should not be modified and it should be copied if it needs to be preserved across several calls to the associated `setInterpolatedTime(double)` method.

      Parameters:
        `secondaryStateIndex` - index of the secondary set, as returned by `ExpandableStatefulODE.addSecondaryEquations(SecondaryEquations)`
      Returns:
        interpolated secondary derivatives at the current interpolation date
      Throws:
        `MaxCountExceededException` - if the number of functions evaluations is exceeded
      Since:
        3.4
      See Also:
        `setInterpolatedTime(double)`, `getInterpolatedState()`, `getInterpolatedDerivatives()`, `getInterpolatedSecondaryState(int)`

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