library: libGraf #include "TGraphAsymmErrors.h"

# TGraphAsymmErrors

class description - source file - inheritance tree (.ps)

## class TGraphAsymmErrors : public TGraph

| Inheritance Chart:

`TObject`

<-

`TNamed`

`TAttLine`

`TAttFill`

`TAttMarker`

<-

`TGraph`

<-

`TGraphAsymmErrors`

        protected:

              Double_t Beta_ab(double a, double b, int k, int N) const
              Double_t Betai(double a, double b, double x) const
              Double_t Brent(double ax, double bx, double cx, double tol, double* xmin) const
          virtual void Efficiency(int k, int N, double conflevel, double& mode, double& low, double& high) const
              Double_t Ibetai(double a, double b, double x) const
              Double_t Interval(double low) const
              Double_t SearchLower(double high, int k, int N, double c) const
              Double_t SearchUpper(double low, int k, int N, double c) const
          virtual void SwapPoints(Int_t pos1, Int_t pos2)

        public:

                             TGraphAsymmErrors()
                             TGraphAsymmErrors(Int_t n)
                             TGraphAsymmErrors(Int_t n, const Float_t* x, const Float_t* y, const Float_t* exl = 0, const Float_t* exh = 0, const Float_t* eyl = 0, const Float_t* eyh = 0)
                             TGraphAsymmErrors(Int_t n, const Double_t* x, const Double_t* y, const Double_t* exl = 0, const Double_t* exh = 0, const Double_t* eyl = 0, const Double_t* eyh = 0)
                             TGraphAsymmErrors(const TGraphAsymmErrors& gr)
                             TGraphAsymmErrors(const TH1* h)
                             TGraphAsymmErrors(const TH1* pass, const TH1* total, Option_t* option)
                     virtual ~TGraphAsymmErrors()
                virtual void Apply(TF1* f)
                virtual void BayesDivide(const TH1* pass, const TH1* total, Option_t* option)
              static TClass* Class()
                virtual void ComputeRange(Double_t& xmin, Double_t& ymin, Double_t& xmax, Double_t& ymax) const
            virtual Double_t GetErrorX(Int_t bin) const
            virtual Double_t GetErrorY(Int_t bin) const
                   Double_t* GetEXhigh() const
                   Double_t* GetEXlow() const
                   Double_t* GetEYhigh() const
                   Double_t* GetEYlow() const
               virtual Int_t InsertPoint()
             virtual TClass* IsA() const
          TGraphAsymmErrors& operator=(const TGraphAsymmErrors&)
                virtual void Paint(Option_t* chopt)
                virtual void Print(Option_t* chopt) const
               virtual Int_t RemovePoint()
               virtual Int_t RemovePoint(Int_t ipoint)
                virtual void SavePrimitive(ofstream& out, Option_t* option)
                virtual void Set(Int_t n)
                virtual void SetPoint(Int_t i, Double_t x, Double_t y)
                virtual void SetPointError(Double_t exl, Double_t exh, Double_t eyl, Double_t eyh)
                virtual void SetPointError(Int_t i, Double_t exl, Double_t exh, Double_t eyl, Double_t eyh)
                virtual void SetPointEXhigh(Int_t i, Double_t exh)
                virtual void SetPointEXlow(Int_t i, Double_t exl)
                virtual void SetPointEYhigh(Int_t i, Double_t eyh)
                virtual void SetPointEYlow(Int_t i, Double_t eyl)
                virtual void ShowMembers(TMemberInspector& insp, char* parent)
                virtual void Streamer(TBuffer& b)
                        void StreamerNVirtual(TBuffer& b)

### Data Members

        protected:

          Double_t* fEXlow   [fNpoints] array of X low errors
          Double_t* fEXhigh  [fNpoints] array of X high errors
          Double_t* fEYlow   [fNpoints] array of Y low errors
          Double_t* fEYhigh  [fNpoints] array of Y high errors

## Class Description

       A TGraphAsymmErrors is a TGraph with assymetric error bars.
       The various format options to draw a TGraphAsymmErrors are explained in
         TGraphAsymmErrors::Paint.

      The picture below has been generated by the following macro:
    ------------------------------------------------------------------------
    {
       gROOT->Reset();
       c1 = new TCanvas("c1","A Simple Graph with error bars",200,10,700,500);

       c1->SetFillColor(42);
       c1->SetGrid();
       c1->GetFrame()->SetFillColor(21);
       c1->GetFrame()->SetBorderSize(12);

       Int_t n = 10;
       Double_t x[n]  = {-0.22, 0.05, 0.25, 0.35, 0.5, 0.61,0.7,0.85,0.89,0.95};
       Double_t y[n]  = {1,2.9,5.6,7.4,9,9.6,8.7,6.3,4.5,1};
       Double_t exl[n] = {.05,.1,.07,.07,.04,.05,.06,.07,.08,.05};
       Double_t eyl[n] = {.8,.7,.6,.5,.4,.4,.5,.6,.7,.8};
       Double_t exh[n] = {.02,.08,.05,.05,.03,.03,.04,.05,.06,.03};
       Double_t eyh[n] = {.6,.5,.4,.3,.2,.2,.3,.4,.5,.6};
       gr = new TGraphAsymmErrors(n,x,y,exl,exh,eyl,eyh);
       gr->SetTitle("TGraphAsymmErrors Example");
       gr->SetMarkerColor(4);
       gr->SetMarkerStyle(21);
       gr->Draw("ALP");

       c1->Update();
    }

/* */

TGraphAsymmErrors(): TGraph()

    *-*-*-*-*-*-*-*-*-*-*TGraphAsymmErrors default constructor*-*-*-*-*-*-*-*-*-*-*-*
    *-*                  =====================================

TGraphAsymmErrors(const TGraphAsymmErrors &gr) : TGraph(gr)

     TGraphAsymmErrors copy constructor

TGraphAsymmErrors(Int_t n) : TGraph(n)

    *-*-*-*-*-*-*-*-*-*-*TGraphAsymmErrors normal constructor*-*-*-*-*-*-*-*-*-*-*-*-*
    *-*                  ====================================

      the arrays are preset to zero

TGraphAsymmErrors(Int_t n, const Float_t *x, const Float_t *y, const Float_t *exl, const Float_t *exh, const Float_t *eyl, const Float_t *eyh) : TGraph(n,x,y)

    *-*-*-*-*-*-*-*-*-*-*TGraphAsymmErrors normal constructor*-*-*-*-*-*-*-*-*-*-*-*-*
    *-*                  ====================================

      if exl,h or eyl,h are null, the corresponding arrays are preset to zero

TGraphAsymmErrors(Int_t n, const Double_t *x, const Double_t *y, const Double_t *exl, const Double_t *exh, const Double_t *eyl, const Double_t *eyh) : TGraph(n,x,y)

    *-*-*-*-*-*-*-*-*-*-*TGraphAsymmErrors normal constructor*-*-*-*-*-*-*-*-*-*-*-*-*
    *-*                  ====================================

      if exl,h or eyl,h are null, the corresponding arrays are preset to zero

TGraphAsymmErrors(const TH1 *h) : TGraph(h)

     TGraphAsymmErrors constructor importing its parameters from the TH1 object passed as argument
     the low and high errors are set to the bin error of the histogram.

TGraphAsymmErrors(const TH1 *pass, const TH1 *total, Option_t *option) : TGraph()

     Creates a TGraphAsymmErrors by dividing two input TH1 histograms:
     pass/total. (see TGraphAsymmErrors::BayesDivide)

~TGraphAsymmErrors()

    *-*-*-*-*-*-*-*-*-*-*TGraphAsymmErrors default destructor*-*-*-*-*-*-*-*-*-*-*-*-*
    *-*                  ===============================

void Apply(TF1 *f)

     apply a function to all data points
     y = f(x,y)

     Errors are calculated as eyh = f(x,y+eyh)-f(x,y) and
     eyl = f(x,y)-f(x,y-eyl)

     Special treatment has to be applied for the functions where the
     role of "up" and "down" is reversed.
     function suggested/implemented by Miroslav Helbich <helbich@mail.desy.de>

void BayesDivide(const TH1 *pass, const TH1 *total, Option_t *option)

     Fills this TGraphAsymmErrors by dividing two input TH1 histograms pass/total.

     Andy Haas (haas@fnal.gov)
     University of Washington

     Method and code directly taken from:
     Marc Paterno (paterno@fnal.gov)
     FNAL/CD

     The input histograms must be filled with weights of 1.
     By default the function does not check this assertion.
     if option "w" is specified, the function will fail if the histograms
     have been filled with weights not equal to 1.

     The assumption is that the entries in "pass" are a
     subset of those in "total". That is, we create an "efficiency"
     graph, where each entry is between 0 and 1, inclusive.
     The resulting graph can be fit to functions, using standard methods:
     graph->Fit("erf")... for instance. (You have to define the erf
     function for yourself for now, sorry.)

     The points are assigned an x value at the center of each histogram bin.
     The y values are #pass/#total, between 0 and 1.
     The x errors span each histogram bin (lowedge->lowedge+width)
     The y errors are the fun part. :)

     The y errors are assigned based on applying Bayes theorem.
     The model is the Binomial distribution, and the "prior" is
     the flat distribution from 0 to 1.
     If there is no data in a bin of the total histogram, no information
     can be obtained for that bin, so no point is made on the graph.

     The complete method and a beautiful discussion can be found here:
     http://home.fnal.gov/~paterno/images/effic.pdf
     And more information is on these pages:
     http://home.fnal.gov/~paterno/probability/localresources.html
     A backup of the main document is here:
     http://www-clued0.fnal.gov/~haas/documents/paterno_effic.pdf

     A 68.3% Confidence Level is used to assign the errors.
     Warning! You should understand, the errors reported are the shortest
     ranges containing 68.3% of the probability distrubution. The errors are
     not exactly Gaussian! The Minuit fitting routines will assume that
     the errors are Gaussian. But this is a reasonable approximation.
     A fit using the full shape of the error distribution for each point
     would be far more difficult to perform.

double Beta_ab(double a, double b, int k, int N) const

     Calculates the fraction of the area under the
     curve x^k*(1-x)^(N-k) between x=a and x=b

double Ibetai(double a, double b, double x) const

     Calculates the incomplete beta function  I_x(a,b); this is
     the incomplete beta function divided by the complete beta function

double Betai(double a, double b, double x) const

     Calculates the incomplete beta function B_x(a,b), as defined
     in Gradshteyn and Ryzhik (4th edition) 8.391

double Brent(double ax, double bx, double cx, double tol, double *xmin) const

     Implementation file for the numerical equation solver library.
     This includes root finding and minimum finding algorithms.
     Adapted from Numerical Recipes in C, 2nd edition.
     Translated to C++ by Marc Paterno

void ComputeRange(Double_t &xmin, Double_t &ymin, Double_t &xmax, Double_t &ymax) const

void Efficiency(int k, int N, double conflevel, double& mode, double& low, double& high) const

     Calculate the shortest central confidence interval containing the required
     probability content.
     Interval(low) returns the length of the interval starting at low
     that contains CONFLEVEL probability. We use Brent's method,
     except in two special cases: when k=0, or when k=N
     Main driver routine
     Author: Marc Paterno

Double_t GetErrorX(Int_t i) const

        This function is called by GraphFitChisquare.
        It returns the error along X at point i.

Double_t GetErrorY(Int_t i) const

        This function is called by GraphFitChisquare.
        It returns the error along Y at point i.

Int_t InsertPoint()

     Insert a new point at the mouse position

double Interval(double low) const

     Return the length of the interval starting at low
     that contains CONFLEVEL of the x^GLOBAL_k*(1-x)^(GLOBAL_N-GLOBAL_k)
     distribution.
     If there is no sufficient interval starting at low, we return 2.0

void Paint(Option_t *option)

     Paint this TGraphAsymmErrors with its current attributes

     by default horizonthal and vertical small lines are drawn at
     the end of the error bars. if option "z" or "Z" is specified,
     these lines are not drawn.

     if option contains ">" an arrow is drawn at the end of the error bars
     if option contains "|>" a full arrow is drawn at the end of the error bars
     the size of the arrow is set to 2/3 of the marker size.

     By default, error bars are drawn. If option "X" is specified,
     the errors are not drawn (TGraph::Paint equivalent).

     if option "[]" is specified only the end vertical/horizonthal lines
     of the error bars are drawn. This option is interesting to superimpose
     systematic errors on top of a graph with statistical errors.

void Print(Option_t *) const

    *-*-*-*-*-*-*-*-*-*-*Print graph and errors values*-*-*-*-*-*-*-*-*-*-*-*
    *-*                  =============================

Int_t RemovePoint()

     Delete point close to the mouse position

Int_t RemovePoint(Int_t ipnt)

     Delete point number ipnt

void SavePrimitive(ofstream &out, Option_t *option)

     Save primitive as a C++ statement(s) on output stream out

double SearchLower(double high, int k, int N, double c) const

     Integrates the binomial distribution with
     parameters k,N, and determines what is the lower edge of the
     integration region which ends at high, and which contains
     probability content c. If a lower limit is found, the value is
     returned. If no solution is found, the -1 is returned.
     check to see if there is any solution by verifying that the integral down
     to the minimum lower limit (0) is greater than c

double SearchUpper(double low, int k, int N, double c) const

     Integrates the binomial distribution with
     parameters k,N, and determines what is the upper edge of the
     integration region which starts at low which contains probability
     content c. If an upper limit is found, the value is returned. If no
     solution is found, -1 is returned.
     check to see if there is any solution by verifying that the integral up
     to the maximum upper limit (1) is greater than c

void Set(Int_t n)

     Set number of points in the graph
     Existing coordinates are preserved
     New coordinates and errors above fNpoints are preset to 0.

void SetPoint(Int_t i, Double_t x, Double_t y)

    *-*-*-*-*-*-*-*-*-*-*Set x and y values for point number i*-*-*-*-*-*-*-*-*
    *-*                  =====================================

void SetPointError(Double_t exl, Double_t exh, Double_t eyl, Double_t eyh)

    *-*-*-*-*-*-*Set ex and ey values for point pointed by the mouse*-*-*-*
    *-*          ===================================================

void SetPointError(Int_t i, Double_t exl, Double_t exh, Double_t eyl, Double_t eyh)

    *-*-*-*-*-*-*-*-*-*-*Set ex and ey values for point number i*-*-*-*-*-*-*-*
    *-*                  =======================================

void SetPointEXlow(Int_t i, Double_t exl)

     Set EXlow for point i

void SetPointEXhigh(Int_t i, Double_t exh)

     Set EXhigh for point i

void SetPointEYlow(Int_t i, Double_t eyl)

     Set EYlow for point i

void SetPointEYhigh(Int_t i, Double_t eyh)

     Set EYhigh for point i

void Streamer(TBuffer &b)

     Stream an object of class TGraphAsymmErrors.

void SwapPoints(Int_t pos1, Int_t pos2)

### Inline Functions

                     Double_t* GetEXlow() const
                     Double_t* GetEXhigh() const
                     Double_t* GetEYlow() const
                     Double_t* GetEYhigh() const
                       TClass* Class()
                       TClass* IsA() const
                          void ShowMembers(TMemberInspector& insp, char* parent)
                          void StreamerNVirtual(TBuffer& b)
            TGraphAsymmErrors& operator=(const TGraphAsymmErrors&)

Author: Rene Brun 03/03/99
Last update: root/graf:$Name: $:$Id: TGraphAsymmErrors.cxx,v 1.40 2004/07/06 14:55:04 brun Exp $
Copyright (C) 1995-2000, Rene Brun and Fons Rademakers. *