```// @(#)root/tmva \$Id: TActivationRadial.h 29122 2009-06-22 06:51:30Z brun \$
// Author: Matt Jachowski

/**********************************************************************************
* Project: TMVA - a Root-integrated toolkit for multivariate data analysis       *
* Package: TMVA                                                                  *
* Web    : http://tmva.sourceforge.net                                           *
*                                                                                *
* Description:                                                                   *
*      Radial basis activation function for TNeuron                              *
*                                                                                *
* Authors (alphabetical):                                                        *
*      Matt Jachowski  <jachowski@stanford.edu> - Stanford University, USA       *
*                                                                                *
*      CERN, Switzerland                                                         *
*                                                                                *
* Redistribution and use in source and binary forms, with or without             *
* modification, are permitted according to the terms listed in LICENSE           *
**********************************************************************************/

//////////////////////////////////////////////////////////////////////////
//                                                                      //
//                                                                      //
// Radial basis activation function for TNeuron                         //
//                                                                      //
//////////////////////////////////////////////////////////////////////////

#ifndef ROOT_TFormula
#include "TFormula.h"
#endif
#ifndef ROOT_TString
#include "TString.h"
#endif

#ifndef ROOT_TMVA_TActivation
#include "TMVA/TActivation.h"
#endif

namespace TMVA {

class TActivationRadial : public TActivation {

public:

// evaluate the activation function
Double_t Eval(Double_t arg);

// evaluate the derivative of the activation function
Double_t EvalDerivative(Double_t arg);

// minimum of the range of the activation function
Double_t GetMin() { return 0; }

// maximum of the range of the activation function
Double_t GetMax() { return 1; }

// expression for the activation function
TString GetExpression();

// writer of function code
virtual void MakeFunction(std::ostream& fout, const TString& fncName);

private:

TFormula* fEqn;                // equation of radial basis function
TFormula* fEqnDerivative;      // equation of derivative

};

} // namespace TMVA

#endif
```