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#include <cmath>#include "RecoTracker/RoadSearchHelixMaker/interface/Dcxprobab.hh"Go to the source code of this file.
Functions | |
| float | Dcxprobab (int &ndof, float &chisq) |
| float Dcxprobab | ( | int & | ndof, | |
| float & | chisq | |||
| ) |
Definition at line 6 of file Dcxprobab.cc.
References funct::exp(), i, m, funct::sqrt(), sum(), and pyDBSRunClass::temp.
00006 { 00007 00008 //constants 00009 static float srtopi=2.0/sqrt(2.0*M_PI); 00010 static float upl=100.0; 00011 00012 float prob=0.0; 00013 if(ndof<=0) {return prob;} 00014 if(chisq<0.0) {return prob;} 00015 if(ndof<=60) { 00016 //full treatment 00017 if(chisq>upl) {return prob;} 00018 float sum=exp(-0.5*chisq); 00019 float term=sum; 00020 00021 int m=ndof/2; 00022 if(2*m==ndof){ 00023 if(m==1){return sum;} 00024 for(int i=2; i<=m;i++){ 00025 term=0.5*term*chisq/(i-1); 00026 sum+=term; 00027 }//(int i=2; i<=m) 00028 return sum; 00029 //even 00030 00031 }else{ 00032 //odd 00033 float srty=sqrt(chisq); 00034 float temp=srty/M_SQRT2; 00035 prob=erfc(temp); 00036 if(ndof==1) {return prob;} 00037 if(ndof==3) {return (srtopi*srty*sum+prob);} 00038 m=m-1; 00039 for(int i=1; i<=m; i++){ 00040 term=term*chisq/(2*i+1); 00041 sum+=term; 00042 }//(int i=1; i<=m; i++) 00043 return (srtopi*srty*sum+prob); 00044 00045 }//(2*m==ndof) 00046 00047 }else{ 00048 //asymtotic Gaussian approx 00049 float srty=sqrt(chisq)-sqrt(ndof-0.5); 00050 if(srty<12.0) {prob=0.5*erfc(srty);}; 00051 return prob; 00052 00053 }//ndof<30 00054 00055 // cannot reach following line; warning on OSF; so comment it out 00056 // return prob; 00057 }//endof Dcxprobab
1.5.4