1 /*=========================================================================
2  *
3  *  Copyright Insight Software Consortium
4  *
5  *  Licensed under the Apache License, Version 2.0 (the "License");
6  *  you may not use this file except in compliance with the License.
7  *  You may obtain a copy of the License at
8  *
9  *         http://www.apache.org/licenses/LICENSE-2.0.txt
10  *
11  *  Unless required by applicable law or agreed to in writing, software
12  *  distributed under the License is distributed on an "AS IS" BASIS,
13  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  *  See the License for the specific language governing permissions and
15  *  limitations under the License.
16  *
17  *=========================================================================*/
18 #ifndef itkKernelFunctionBase_h
19 #define itkKernelFunctionBase_h
20 
21 #include "itkFunctionBase.h"
22 #include "itkConceptChecking.h"
23 #include "itkNumericTraits.h"
24 #include "itkMath.h"
25 
26 namespace itk
27 {
28 /** \class KernelFunctionBase
29  * \brief Kernel used for density estimation and nonparameteric regression.
30  *
31  * This class encapsulates the smoothing kernel used for statistical density
32  * estimation and nonparameteric regression. The basic idea of the kernel
33  * approach is to weight observations by a smooth function (the kernel)
34  * to created a smoothed approximation.
35  *
36  * Reference:
37  * Silverman, B. W. (1986) Density Estimation. London: Chapman and Hall.
38  *
39  * \ingroup Functions
40  * \ingroup ITKCommon
41  */
42 template< typename TRealValueType = double >
43 class KernelFunctionBase:public FunctionBase< TRealValueType, TRealValueType >
44 {
45 public:
46   /** Standard class type aliases. */
47   using Self = KernelFunctionBase;
48   using Superclass = FunctionBase< TRealValueType, TRealValueType >;
49   using Pointer = SmartPointer< Self >;
50   using ConstPointer = SmartPointer< const Self >;
51 
52   using RealType = TRealValueType;
53 
54   /** Run-time type information (and related methods). */
55   itkTypeMacro(KernelFunctionBase, FunctionBase);
56 
57   /** Evaluate the function. Subclasses must implement this. */
58   TRealValueType Evaluate(const TRealValueType & u) const override = 0;
59 
60 #ifdef ITK_USE_CONCEPT_CHECKING
61     // Begin concept checking
62     itkConceptMacro( TRealValueTypeIsFloatingPointCheck,
63                          ( Concept::IsFloatingPoint< TRealValueType > ) );
64       // End concept checking
65 #endif
66 
67 protected:
68   KernelFunctionBase() = default;
69   ~KernelFunctionBase() override = default;
PrintSelf(std::ostream & os,Indent indent)70   void PrintSelf(std::ostream & os, Indent indent) const override
71   { Superclass::PrintSelf(os, indent); }
72 };
73 } // end namespace itk
74 
75 #endif // itkKernelFunctionBase_h
76