PixelTrackFitting/src/ParabolaFit.h

0001 #ifndef RecoTracker_PixelTrackFitting_src_ParabolaFit_h
0002 #define RecoTracker_PixelTrackFitting_src_ParabolaFit_h
0003
0004 #include <vector>
0005
0006 /** The parabola fit
0007     y = parA + parB * x + parC * x*x
0008     see: R.L. Gluckstern, NIM 24 (1963) 381
0009  */
0010
0011 class ParabolaFit {
0012 public:
0013   struct Result {
0014     double parA, parB, parC;
0015     double varAA, varBB, varCC, varAB, varAC, varBC;
0016   };
0017   ParabolaFit() : doErr(true), hasFixedParC(false), hasValues(false), hasErrors(false), hasWeights(true) {}
0018
0019   void addPoint(double x, double y);
0020   void addPoint(double x, double y, double weight);
0021
0022   void skipErrorCalculationByDefault() { doErr = false; }
0023   void fixParC(double val) {
0024     hasFixedParC = true;
0025     theResult.parC = val;
0026   }
0027
0028   const Result& result(bool doErrors) const;
0029
0030   double parA() const {
0031     if (!hasValues)
0032       result(doErr);
0033     return theResult.parA;
0034   }
0035   double parB() const {
0036     if (!hasValues)
0037       result(doErr);
0038     return theResult.parB;
0039   }
0040   double parC() const {
0041     if (!hasValues)
0042       result(doErr);
0043     return theResult.parC;
0044   }
0045   double varAA() const {
0046     if (!hasErrors)
0047       result(true);
0048     return theResult.varAA;
0049   }
0050   double varBB() const {
0051     if (!hasErrors)
0052       result(true);
0053     return theResult.varBB;
0054   }
0055   double varCC() const {
0056     if (!hasErrors)
0057       result(true);
0058     return theResult.varCC;
0059   }
0060   double varAB() const {
0061     if (!hasErrors)
0062       result(true);
0063     return theResult.varAB;
0064   }
0065   double varAC() const {
0066     if (!hasErrors)
0067       result(true);
0068     return theResult.varAC;
0069   }
0070   double varBC() const {
0071     if (!hasErrors)
0072       result(true);
0073     return theResult.varBC;
0074   }
0075
0076   double chi2() const;
0077   int dof() const;
0078
0079 private:
0080   struct Column {
0081     double r1;
0082     double r2;
0083     double r3;
0084   };
0085   double det(const Column& c1, const Column& c2, const Column& c3) const;
0086   double det(const Column& c1, const Column& c2) const;
0087
0088   double fun(double x) const;
0089
0090 private:
0091   struct Point {
0092     double x;
0093     double y;
0094     mutable double w;
0095   };
0096   std::vector<Point> points;
0097   bool doErr, hasFixedParC;
0098   mutable bool hasValues, hasErrors;
0099   bool hasWeights;
0100   mutable Result theResult;
0101 };
0102
0103 #endif