library: libHist #include "TGraph2D.h"

# TGraph2D

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

## class TGraph2D : public TNamed, public TAttLine, public TAttFill, public TAttMarker

| Inheritance Chart:

`TObject`

<-

`TNamed`

`TAttLine`

`TAttFill`

`TAttMarker`

<-

`TGraph2D`

<-

`TGraph2DErrors` |

        protected:

          void Build(Int_t n)

        public:

                           TGraph2D()
                           TGraph2D(Int_t n)
                           TGraph2D(Int_t n, Int_t* x, Int_t* y, Int_t* z)
                           TGraph2D(Int_t n, Float_t* x, Float_t* y, Float_t* z)
                           TGraph2D(Int_t n, Double_t* x, Double_t* y, Double_t* z)
                           TGraph2D(TH2* h2)
                           TGraph2D(const char* name, const char* title, Int_t n, Double_t* x, Double_t* y, Double_t* z)
                           TGraph2D(const char* filename, const char* format = "%lg %lg %lg", Option_t* option = "")
                           TGraph2D(const TGraph2D&)
                  TGraph2D operator=(const TGraph2D&)
                   virtual ~TGraph2D()
            static TClass* Class()
             virtual Int_t DistancetoPrimitive(Int_t px, Int_t py)
              virtual void Draw(Option_t* option = "")
              virtual void ExecuteEvent(Int_t event, Int_t px, Int_t py)
          virtual TObject* FindObject(const char* name) const
          virtual TObject* FindObject(const TObject* obj) const
             virtual Int_t Fit(const char* formula, Option_t* option = "", Option_t* goption = "")
             virtual Int_t Fit(TF2* f2, Option_t* option = "", Option_t* goption = "")
                    TList* GetContourList(Double_t contour)
               TDirectory* GetDirectory() const
          virtual Double_t GetErrorX(Int_t bin) const
          virtual Double_t GetErrorY(Int_t bin) const
          virtual Double_t GetErrorZ(Int_t bin) const
                     TH2D* GetHistogram(Option_t* option = "")
                    TList* GetListOfFunctions() const
                  Double_t GetMargin() const
                     Int_t GetN() const
                     Int_t GetNpx() const
                     Int_t GetNpy() const
                 Double_t* GetX() const
                    TAxis* GetXaxis() const
                  Double_t GetXmax() const
                  Double_t GetXmin() const
                 Double_t* GetY() const
                    TAxis* GetYaxis() const
                  Double_t GetYmax() const
                  Double_t GetYmin() const
                 Double_t* GetZ() const
                    TAxis* GetZaxis() const
                  Double_t GetZmax() const
                  Double_t GetZmin() const
                  Double_t Interpolate(Double_t x, Double_t y)
           virtual TClass* IsA() const
              virtual void Paint(Option_t* option = "")
                      TH1* Project(Option_t* option = "x") const
                     Int_t RemovePoint(Int_t ipoint)
              virtual void SavePrimitive(ofstream& out, Option_t* option)
              virtual void SetDirectory(TDirectory* dir)
              virtual void SetHistogram(TH2* h)
                      void SetMargin(Double_t m = 0.1)
                      void SetMarginBinsContent(Double_t z = 0.)
                      void SetMaximum(Double_t maximum = -1111)
                      void SetMaxIter(Int_t n = 100000)
                      void SetMinimum(Double_t minimum = -1111)
              virtual void SetName(const char* name)
                      void SetNpx(Int_t npx = 40)
                      void SetNpy(Int_t npx = 40)
                      void SetPoint(Int_t point, Double_t x, Double_t y, Double_t z)
              virtual void SetTitle(const char* title = "")
              virtual void ShowMembers(TMemberInspector& insp, char* parent)
              virtual void Streamer(TBuffer& b)
                      void StreamerNVirtual(TBuffer& b)

### Data Members

        private:

          Bool_t kUserHisto  True when SetHistogram has been called

        protected:

                         Int_t fNpoints    Number of points in the data set
                         Int_t fNpx        Number of bins along X in fHistogram
                         Int_t fNpy        Number of bins along Y in fHistogram
                         Int_t fMaxIter    Maximum number of iterations to find Delaunay t>
                         Int_t fSize       !Real size of fX, fY and fZ
                     Double_t* fX          [fNpoints]
                     Double_t* fY          [fNpoints] Data set to be plotted
                     Double_t* fZ          [fNpoints]
                      Double_t fMinimum    Minimum value for plotting along z
                      Double_t fMaximum    Maximum value for plotting along z
                      Double_t fMargin     Extra space (in %) around interpolated area for fHistogram
                      Double_t fZout       fHistogram bin height for points lying outside the interpolated area
                        TList* fFunctions  Pointer to list of functions (fits and user)
                         TH2D* fHistogram  !2D histogram of z values linearly interpolated
                   TDirectory* fDirectory  !Pointer to directory holding this 2D graph
          TVirtualHistPainter* fPainter    !pointer to histogram painter

## Class Description

     A Graph2D is a graphics object made of three arrays X, Y and Z with the same
     number of points each.

     This class has different constructors:

     1) With an array's dimension and three arrays x, y, and z:

        TGraph2D *g = new TGraph2D(n, x, y, z);

        x, y, z arrays can be doubles, floats, or ints.

     2) With an array's dimension only:

        TGraph2D *g = new TGraph2D(n);

        The internal arrays are then filled with SetPoint. The following line
        fills the the internal arrays at the position "i" with the values x,y,z.

        g->SetPoint(i, x, y, z);

     3) Without parameters:

        TGraph2D *g = new TGraph2D();

        again SetPoint must be used to fill the internal arrays.

     4) From a file:

        TGraph2D *g = new TGraph2D("graph.dat");

        Arrays are read from the ASCII file "graph.dat" according to a specifies
        format. The format's default value is "%lg %lg %lg"

     Note that in any of these three cases, SetPoint can be used to change a data
     point or add a new one. If the data point index (i) is greater than the
     current size of the internal arrays, they are automatically extended.

     Specific drawing options can be used to paint a TGraph2D:
       "TRI"  : The Delaunay triangles are drawn using filled area.
                An hidden surface drawing technique is used. The surface is
                painted with the current fill area color. The edges of each
                triangles are painted with the current line color.
       "TRIW" : The Delaunay triangles are drawn as wire frame
       "TRI1" : The Delaunay triangles are painted with color levels. The edges
                of each triangles are painted with the current line color.
       "TRI2" : the Delaunay triangles are painted with color levels.
       "P"    : Draw a marker at each vertex
       "P0"   : Draw a circle at each vertex. Each circle background is white.

     A TGraph2D can be also drawn with ANY options valid to draw a 2D histogram.

     When a TGraph2D is drawn with one of the 2D histogram drawing option,
     a intermediate 2D histogram is filled using the Delaunay triangles
     technique to interpolate the data set.

     TGraph2D linearly interpolate a Z value for any (X,Y) point given some
     existing (X,Y,Z) points. The existing (X,Y,Z) points can be randomly
     scattered. The algorithm works by joining the existing points to make
     Delaunay triangles in (X,Y). These are then used to define flat planes
     in (X,Y,Z) over which to interpolate. The interpolated surface thus takes
     the form of tessellating triangles at various angles. Output can take the
     form of a 2D histogram or a vector. The triangles found can be drawn in 3D.

     This software cannot be guaranteed to work under all circumstances. They
     were originally written to work with a few hundred points in an XY space
     with similar X and Y ranges.

      The picture below has been generated by the following macro:

    {
       TCanvas *c = new TCanvas("c","Graph2D example",0,0,700,600);
       Double_t x, y, z, P = 6.;
       Int_t np = 200;
       TGraph2D *dt = new TGraph2D();
       TRandom *r = new TRandom();
       for (Int_t N=0; N<np; N++) {
          x = 2*P*(r->Rndm(N))-P;
          y = 2*P*(r->Rndm(N))-P;
          z = (sin(x)/x)*(sin(y)/y)+0.2;
          dt->SetPoint(N,x,y,z);
       }
       gStyle->SetPalette(1);
       dt->Draw("surf1");
    }

/* */

     A more complete example can be find in $ROOTSYS/tutorial/graph2dfit.C. It
     produces the following output:

/* */

     Definition of Delaunay triangulation (After B. Delaunay):
     For a set S of points in the Euclidean plane, the unique triangulation DT(S)
     of S such that no point in S is inside the circumcircle of any triangle in
     DT(S). DT(S) is the dual of the Voronoi diagram of S.
     If n is the number of points in S, the Voronoi diagram of S is the partitioning
     of the plane containing S points into n convex polygons such that each polygon
     contains exactly one point and every point in a given polygon is closer to its
     central point than to any other. A Voronoi diagram is sometimes also known as
     a Dirichlet tessellation.

/*
This applet gives a nice practical view of Delaunay triangulation and Voronoi diagram. */

TGraph2D() : TNamed("Graph2D","Graph2D"), TAttLine(1,1,1), TAttFill(0,1001), TAttMarker(), fNpoints(0)

     Graph2D default constructor

TGraph2D(Int_t n, Int_t *x, Int_t *y, Int_t *z) : TNamed("Graph2D","Graph2D"), TAttLine(1,1,1), TAttFill(0,1001), TAttMarker(), fNpoints(n)

     Graph2D constructor with three vectors of ints as input.

TGraph2D(Int_t n, Float_t *x, Float_t *y, Float_t *z) : TNamed("Graph2D","Graph2D"), TAttLine(1,1,1), TAttFill(0,1001), TAttMarker(), fNpoints(n)

     Graph2D constructor with three vectors of floats as input.

TGraph2D(Int_t n, Double_t *x, Double_t *y, Double_t *z) : TNamed("Graph2D","Graph2D"), TAttLine(1,1,1), TAttFill(0,1001), TAttMarker(), fNpoints(n)

     Graph2D constructor with three vectors of doubles as input.

TGraph2D(TH2 *h2) : TNamed("Graph2D","Graph2D"), TAttLine(1,1,1), TAttFill(0,1001), TAttMarker(), fNpoints(0)

     Graph2D constructor with a TH2 (h2) as input.
     Only the h2's bins within the X and Y axis ranges are used.

TGraph2D(const char *name,const char *title, Int_t n, Double_t *x, Double_t *y, Double_t *z) : TNamed(name,title), TAttLine(1,1,1), TAttFill(0,1001), TAttMarker(), fNpoints(n)

     Graph2D constructor with name, title and three vectors of doubles as input.
     name   : name of 2D graph (avoid blanks)
     title  : 2D graph title
              if title is of the form "stringt;stringx;stringy;stringz"
              the 2D graph title is set to stringt, the x axis title to stringy,
              the y axis title to stringy,etc

TGraph2D(Int_t n) : TNamed("Graph2D","Graph2D"), TAttLine(1,1,1), TAttFill(0,1001), TAttMarker(), fNpoints(0)

     Graph2D constructor. The arrays fX, fY and fZ should be filled via
     calls to SetPoint

TGraph2D(const char *filename, const char *format, Option_t *) : TNamed("Graph2D",filename), TAttLine(1,1,1), TAttFill(0,1001), TAttMarker(), fNpoints(0)

     Graph2D constructor reading input from filename
     filename is assumed to contain at least three columns of numbers

TGraph2D(const TGraph2D &g) : TNamed(g), TAttLine(g), TAttFill(g), TAttMarker(g)

     Graph2D copy constructor.

~TGraph2D()

     TGraph2D destructor.

void Build(Int_t n)

     Creates the 2D graph basic data structure

Int_t DistancetoPrimitive(Int_t px, Int_t py)

     Computes distance from point px,py to a graph

void Draw(Option_t *option)

     Specific drawing options can be used to paint a TGraph2D:
       "TRI"  : The Delaunay triangles are drawn using filled area.
                An hidden surface drawing technique is used. The surface is
                painted with the current fill area color. The edges of each
                triangles are painted with the current line color.
       "TRIW" : The Delaunay triangles are drawn as wire frame
       "TRI1" : The Delaunay triangles are painted with color levels. The edges
                of each triangles are painted with the current line color.
       "TRI2" : the Delaunay triangles are painted with color levels.
       "P"    : Draw a marker at each vertex
       "P0"   : Draw a circle at each vertex. Each circle background is white.

     A TGraph2D can be also drawn with ANY options valid to draw a 2D histogram.

     When a TGraph2D is drawn with one of the 2D histogram drawing option,
     a intermediate 2D histogram is filled using the Delaunay triangles
     technique to interpolate the data set.

void ExecuteEvent(Int_t event, Int_t px, Int_t py)

     Executes action corresponding to one event

TObject* FindObject(const char *name) const

     search object named name in the list of functions

TObject* FindObject(const TObject *obj) const

     search object obj in the list of functions

Int_t Fit(const char *fname, Option_t *option, Option_t *)

     Fits this graph with function with name fname
     Predefined functions such as gaus, expo and poln are automatically
     created by ROOT.
     fname can also be a formula, accepted by the linear fitter (linear parts divided
     by "++" sign), for example "x++sin(x)" for fitting "[0]*x+[1]*sin(x)"

Int_t Fit(TF2 *f2, Option_t *option, Option_t *)

     Fits this 2D graph with function f2

      f2 is an already predefined function created by TF2.
      Predefined functions such as gaus, expo and poln are automatically
      created by ROOT.

      The list of fit options is given in parameter option.
         option = "W"  Set all errors to 1
                = "U" Use a User specified fitting algorithm (via SetFCN)
                = "Q" Quiet mode (minimum printing)
                = "V" Verbose mode (default is between Q and V)
                = "R" Use the Range specified in the function range
                = "N" Do not store the graphics function, do not draw
                = "0" Do not plot the result of the fit. By default the fitted function
                      is drawn unless the option"N" above is specified.
                = "+" Add this new fitted function to the list of fitted functions
                      (by default, any previous function is deleted)
                = "C" In case of linear fitting, not calculate the chisquare
                      (saves time)
                = "ROB" In case of linear fitting, compute the LTS regression
                         coefficients (robust(resistant) regression), using
                         the default fraction of good points
                  "ROB=0.x" - compute the LTS regression coefficients, using
                               0.x as a fraction of good points

      In order to use the Range option, one must first create a function
      with the expression to be fitted. For example, if your graph2d
      has a defined range between -4 and 4 and you want to fit a gaussian
      only in the interval 1 to 3, you can do:
           TF2 *f2 = new TF2("f2","gaus",1,3);
           graph2d->Fit("f2","R");

      Setting initial conditions
      ==========================
      Parameters must be initialized before invoking the Fit function.
      The setting of the parameter initial values is automatic for the
      predefined functions : poln, expo, gaus. One can however disable
      this automatic computation by specifying the option "B".
      You can specify boundary limits for some or all parameters via
           f2->SetParLimits(p_number, parmin, parmax);
      if parmin>=parmax, the parameter is fixed
      Note that you are not forced to fix the limits for all parameters.
      For example, if you fit a function with 6 parameters, you can do:
        func->SetParameters(0,3.1,1.e-6,0.1,-8,100);
        func->SetParLimits(4,-10,-4);
        func->SetParLimits(5, 1,1);
      With this setup, parameters 0->3 can vary freely
      Parameter 4 has boundaries [-10,-4] with initial value -8
      Parameter 5 is fixed to 100.

      Fit range
      =========
      The fit range can be specified in two ways:
        - specify rxmax > rxmin (default is rxmin=rxmax=0)
        - specify the option "R". In this case, the function will be taken
          instead of the full graph range.

      Changing the fitting function
      =============================
      By default the fitting function Graph2DFitChisquare is used.
      To specify a User defined fitting function, specify option "U" and
      call the following functions:
        TVirtualFitter::Fitter(mygraph)->SetFCN(MyFittingFunction)
      where MyFittingFunction is of type:
      extern void MyFittingFunction(Int_t &npar, Double_t *gin, Double_t &f, Double_t *u, Int_t flag);

      Associated functions
      ====================
      One or more object (typically a TF2*) can be added to the list
      of functions (fFunctions) associated to each graph.
      When TGraph::Fit is invoked, the fitted function is added to this list.
      Given a graph gr, one can retrieve an associated function
      with:  TF2 *myfunc = gr->GetFunction("myfunc");

      Access to the fit results
      =========================
      If the graph is made persistent, the list of
      associated functions is also persistent. Given a pointer (see above)
      to an associated function myfunc, one can retrieve the function/fit
      parameters with calls such as:
        Double_t chi2 = myfunc->GetChisquare();
        Double_t par0 = myfunc->GetParameter(0); //value of 1st parameter
        Double_t err0 = myfunc->GetParError(0);  //error on first parameter

      Fit Statistics
      ==============
      You can change the statistics box to display the fit parameters with
      the TStyle::SetOptFit(mode) method. This mode has four digits.
      mode = pcev  (default = 0111)
        v = 1;  print name/values of parameters
        e = 1;  print errors (if e=1, v must be 1)
        c = 1;  print Chisquare/Number of degress of freedom
        p = 1;  print Probability

      For example: gStyle->SetOptFit(1011);
      prints the fit probability, parameter names/values, and errors.
      You can change the position of the statistics box with these lines
      (where g is a pointer to the TGraph):

      Root > TPaveStats *st = (TPaveStats*)g->GetListOfFunctions()->FindObject("stats")
      Root > st->SetX1NDC(newx1); //new x start position
      Root > st->SetX2NDC(newx2); //new x end position

TAxis* GetXaxis() const

     Get x axis of the graph.

TAxis* GetYaxis() const

     Get y axis of the graph.

TAxis* GetZaxis() const

     Get z axis of the graph.

TList* GetContourList(Double_t contour)

     Returns the X and Y graphs building a contour. A contour level may
     consist in several parts not connected to each other. This function
     returns them in a graphs' list.

Double_t GetErrorX(Int_t) const

     This function is called by Graph2DFitChisquare.
     It always returns a negative value. Real implementation in TGraph2DErrors

Double_t GetErrorY(Int_t) const

     This function is called by Graph2DFitChisquare.
     It always returns a negative value. Real implementation in TGraph2DErrors

Double_t GetErrorZ(Int_t) const

     This function is called by Graph2DFitChisquare.
     It always returns a negative value. Real implementation in TGraph2DErrors

TH2D* GetHistogram(Option_t *option)

     By default returns a pointer to the Delaunay histogram. If fHistogram
     doesn't exist, books the 2D histogram fHistogram with a margin around
     the hull. Calls TGraphDelaunay::Interpolate at each bin centre to build up
     an interpolated 2D histogram.
     If the "empty" option is selected, returns an empty histogram booked with
     the limits of fX, fY and fZ. This option is used when the data set is
     drawn with markers only. In that particular case there is no need to
     find the Delaunay triangles.

Double_t GetXmax() const

     Returns the X maximum

Double_t GetXmin() const

     Returns the X minimum

Double_t GetYmax() const

     Returns the Y maximum

Double_t GetYmin() const

     Returns the Y minimum

Double_t GetZmax() const

     Returns the Z maximum

Double_t GetZmin() const

     Returns the Z minimum

Double_t Interpolate(Double_t x, Double_t y)

     Finds the z value at the position (x,y) thanks to
     the Delaunay interpolation.

void Paint(Option_t *option)

     Paints this 2D graph with its current attributes

TH1* Project(Option_t *option) const

     Projects a 2-d graph into 1 or 2-d histograms depending on the
     option parameter
     option may contain a combination of the characters x,y,z
     option = "x" return the x projection into a TH1D histogram
     option = "y" return the y projection into a TH1D histogram
     option = "xy" return the x versus y projection into a TH2D histogram
     option = "yx" return the y versus x projection into a TH2D histogram

Int_t RemovePoint(Int_t ipoint)

     Deletes point number ipoint

void SavePrimitive(ofstream &out, Option_t *option)

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

void SetDirectory(TDirectory *dir)

     By default when an 2D graph is created, it is added to the list
     of 2D graph objects in the current directory in memory.
     Remove reference to this 2D graph from current directory and add
     reference to new directory dir. dir can be 0 in which case the
     2D graph does not belong to any directory.

void SetHistogram(TH2 *h)

     Sets the histogram to be filled

void SetMargin(Double_t m)

     Sets the extra space (in %) around interpolated area for the 2D histogram

void SetMarginBinsContent(Double_t z)

     Sets the histogram bin height for points lying outside the TGraphDelaunay
     convex hull ie: the bins in the margin.

void SetMaximum(Double_t maximum)

void SetMinimum(Double_t minimum)

void SetName(const char *name)

     Changes the name of this 2D graph

void SetNpx(Int_t npx)

     Sets the number of bins along X used to draw the function

void SetNpy(Int_t npy)

     Sets the number of bins along Y used to draw the function

void SetPoint(Int_t n, Double_t x, Double_t y, Double_t z)

     Sets point number n.
     If n is greater than the current size, the arrays are automatically
     extended.

void SetTitle(const char* title)

     Sets graph title

void Streamer(TBuffer &b)

     Stream a class object

### Inline Functions

               TGraph2D operator=(const TGraph2D&)
            TDirectory* GetDirectory() const
                  Int_t GetNpx() const
                  Int_t GetNpy() const
                 TList* GetListOfFunctions() const
               Double_t GetMargin() const
                  Int_t GetN() const
              Double_t* GetX() const
              Double_t* GetY() const
              Double_t* GetZ() const
                   void SetMaxIter(Int_t n = 100000)
                TClass* Class()
                TClass* IsA() const
                   void ShowMembers(TMemberInspector& insp, char* parent)
                   void StreamerNVirtual(TBuffer& b)

Author: Olivier Couet
Last update: root/hist:$Name: $:$Id: TGraph2D.cxx,v 1.00
Copyright (C) 1995-2000, Rene Brun and Fons Rademakers. *