exponential.H

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License
    This file is part of OpenFOAM.
 
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Class
    Foam::distributions::exponential
 
Description
    Exponential distribution, scaled so that it spans between a specified
    minimum and maximum value, rather than from zero to infinity
 
    \f[
        PDF(x) = \lambda \exp(- \lambda x)
    \f]
 
Usage
    Example usage:
    \verbatim
    {
        type    exponential;
        Q       3;
        min     0.01;
        max     0.5;
        lambda  3;
    }
    \endverbatim
 
SourceFiles
    exponential.C
 
See also
    Foam::distribution
 
\*---------------------------------------------------------------------------*/
 
#ifndef exponential_H
#define exponential_H
 
#include "unintegrable.H"
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
namespace distributions
{
 
/*---------------------------------------------------------------------------*\
                        Class exponential Declaration
\*---------------------------------------------------------------------------*/
 
class exponential
:
    public FieldDistribution<unintegrableForNonZeroQ, exponential>
{
    // Private Data
 
        //- Minimum value
        const scalar min_;
 
        //- Maximum value
        const scalar max_;
 
        //- Parameter
        const scalar lambda_;
 
 
    // Private Member Functions
 
        //- Return values of the un-normalised PDF for the given size exponent
        //  and x-coordinates.
        virtual tmp<scalarField> phi
        (
            const label q,
            const scalarField& x
        ) const;
 
        //- Return values of the un-normalised CDF for the given size exponent
        //  and x-coordinates.
        virtual tmp<scalarField> Phi
        (
            const label q,
            const scalarField& x
        ) const;
 
 
public:
 
    //- Runtime type information
    TypeName("exponential");
 
 
    // Constructors
 
        //- Construct from a dictionary
        exponential
        (
            const unitConversion& units,
            const dictionary& dict,
            const label sampleQ,
            randomGenerator&& rndGen
        );
 
        //- Construct copy
        exponential(const exponential& d, const label sampleQ);
 
        //- Construct and return a clone
        virtual autoPtr<distribution> clone(const label sampleQ) const
        {
            return autoPtr<distribution>(new exponential(*this, sampleQ));
        }
 
 
    //- Destructor
    virtual ~exponential();
 
 
    // Member Functions
 
        //- Sample the distribution
        virtual scalar sample() const;
 
        //- Sample the distribution
        using FieldDistribution<unintegrableForNonZeroQ, exponential>::sample;
 
        //- Return the minimum value
        virtual scalar min() const;
 
        //- Return the maximum value
        virtual scalar max() const;
 
        //- Write to a stream
        virtual void write(Ostream& os, const unitConversion& units) const;
 
        //- Return coordinates to plot across the range of the distribution
        virtual tmp<scalarField> x(const label n) const;
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace distributions
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //