SecondaryEquations (Apache Commons Math 4.0-beta1)

```
public interface SecondaryEquations
```
This interface allows users to add secondary differential equations to a primary set of differential equations.
In some cases users may need to integrate some problem-specific equations along with a primary set of differential equations. One example is optimal control where adjoined parameters linked to the minimized hamiltonian must be integrated.

This interface allows users to add such equations to a primary set of first order differential equations thanks to the ExpandableStatefulODE.addSecondaryEquations(SecondaryEquations) method.

Since:

3.0

See Also:

ExpandableStatefulODE

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`void`	`computeDerivatives(double t, double[] primary, double[] primaryDot, double[] secondary, double[] secondaryDot)`	Compute the derivatives related to the secondary state parameters.
`int`	`getDimension()`	Get the dimension of the secondary state parameters.

- Method Detail
  - getDimension
```
int getDimension()
```
    Get the dimension of the secondary state parameters.
    
    Returns:
    
    dimension of the secondary state parameters
  - computeDerivatives
```
void computeDerivatives(double t,
                        double[] primary,
                        double[] primaryDot,
                        double[] secondary,
                        double[] secondaryDot)
                 throws MaxCountExceededException,
                        DimensionMismatchException
```
    Compute the derivatives related to the secondary state parameters.
    
    Parameters:
    
    t - current value of the independent time variable
    
    primary - array containing the current value of the primary state vector
    
    primaryDot - array containing the derivative of the primary state vector
    
    secondary - array containing the current value of the secondary state vector
    
    secondaryDot - placeholder array where to put the derivative of the secondary state vector
    
    Throws:
    
    MaxCountExceededException - if the number of functions evaluations is exceeded
    
    DimensionMismatchException - if arrays dimensions do not match equations settings