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TSpline1.cxx
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1// @(#)root/tmva $Id$
2// Author: Andreas Hoecker, Joerg Stelzer, Helge Voss
3
4/**********************************************************************************
5 * Project: TMVA - a Root-integrated toolkit for multivariate data analysis *
6 * Package: TMVA *
7 * Class : TSpline1 *
8 * Web : http://tmva.sourceforge.net *
9 * *
10 * Description: *
11 * Implementation (see header for description) *
12 * *
13 * Authors (alphabetical): *
14 * Andreas Hoecker <Andreas.Hocker@cern.ch> - CERN, Switzerland *
15 * Helge Voss <Helge.Voss@cern.ch> - MPI-K Heidelberg, Germany *
16 * Kai Voss <Kai.Voss@cern.ch> - U. of Victoria, Canada *
17 * *
18 * Copyright (c) 2005: *
19 * CERN, Switzerland *
20 * U. of Victoria, Canada *
21 * MPI-K Heidelberg, Germany *
22 * *
23 * Redistribution and use in source and binary forms, with or without *
24 * modification, are permitted according to the terms listed in LICENSE *
25 * (http://tmva.sourceforge.net/LICENSE) *
26 **********************************************************************************/
27
28/*! \class TMVA::TSpline1
29\ingroup TMVA
30Linear interpolation of TGraph
31*/
32
33#include "TMVA/TSpline1.h"
34
35#include "TGraph.h"
36#include "TMath.h"
37
39
40////////////////////////////////////////////////////////////////////////////////
41/// constructor from TGraph
42/// TSpline is a TNamed object
43
44TMVA::TSpline1::TSpline1( const TString& title, TGraph* theGraph )
45: fGraph( theGraph )
46{
47 SetNameTitle( title, title );
48}
49
50////////////////////////////////////////////////////////////////////////////////
51/// destructor
52
54{
55 if (fGraph) delete fGraph; // ROOT's spline classes also own the TGraph
56}
57
58////////////////////////////////////////////////////////////////////////////////
59/// returns linearly interpolated TGraph entry around x
60
62{
63 Int_t ibin = TMath::BinarySearch( fGraph->GetN(),
64 fGraph->GetX(),
65 x );
66 Int_t nbin = fGraph->GetN();
67
68 // sanity checks
69 if (ibin < 0 ) ibin = 0;
70 if (ibin >= nbin) ibin = nbin - 1;
71
72 Int_t nextbin = ibin;
73 if ((x > fGraph->GetX()[ibin] && ibin != nbin-1) || ibin == 0)
74 nextbin++;
75 else
76 nextbin--;
77
78 // linear interpolation
79 Double_t dx = fGraph->GetX()[ibin] - fGraph->GetX()[nextbin];
80 Double_t dy = fGraph->GetY()[ibin] - fGraph->GetY()[nextbin];
81 return fGraph->GetY()[ibin] + (x - fGraph->GetX()[ibin]) * dy/dx;
82}
83
84////////////////////////////////////////////////////////////////////////////////
85/// no coefficients to precompute
86
88{
89}
90
91////////////////////////////////////////////////////////////////////////////////
92/// no knots
93
94void TMVA::TSpline1::GetKnot( Int_t /* i*/, Double_t& /*x*/, Double_t& /*y*/ ) const
95{
96}
int Int_t
Definition: RtypesCore.h:45
double Double_t
Definition: RtypesCore.h:59
#define ClassImp(name)
Definition: Rtypes.h:364
A TGraph is an object made of two arrays X and Y with npoints each.
Definition: TGraph.h:41
Linear interpolation of TGraph.
Definition: TSpline1.h:43
TSpline1(const TString &title, TGraph *theGraph)
constructor from TGraph TSpline is a TNamed object
Definition: TSpline1.cxx:44
virtual void GetKnot(Int_t i, Double_t &x, Double_t &y) const
no knots
Definition: TSpline1.cxx:94
virtual ~TSpline1(void)
destructor
Definition: TSpline1.cxx:53
virtual void BuildCoeff(void)
no coefficients to precompute
Definition: TSpline1.cxx:87
virtual Double_t Eval(Double_t x) const
returns linearly interpolated TGraph entry around x
Definition: TSpline1.cxx:61
virtual void SetNameTitle(const char *name, const char *title)
Set all the TNamed parameters (name and title).
Definition: TNamed.cxx:154
Basic string class.
Definition: TString.h:136
Double_t x[n]
Definition: legend1.C:17
Long64_t BinarySearch(Long64_t n, const T *array, T value)
Definition: TMathBase.h:278