TF12.cxx

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// @(#)root/hist:$Id$
// Author: Rene Brun   05/04/2003
 
/*************************************************************************
 * Copyright (C) 1995-2003, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/
 
#include "TF12.h"
#include "TH1.h"
#include "TVirtualPad.h"
 
#include <ostream>
 
/** \class TF12
    \ingroup Functions
 A projection of a TF2 along X or Y
 
It has the same behaviour as a TF1
 
Example of a function
 
Begin_Macro(source)
{
    auto f2 = new TF2("f2","sin(x)*sin(y)/(x*y)",0,5,0,5);
    auto f12 = new TF12("f12",f2,0.1,"y");
    f12->Draw();
}
End_Macro
 
Side note: TF12 derives from TF1 but it does not store the number of parameters:
so `GetNpar()` will be 0. Instead, it contains a private member pointing to the
original TF2. Hence, one should not modify the (zero) parameters of the TF12
but rather modify the original TF2 the TF12 is pointing to.
 
*/
 
////////////////////////////////////////////////////////////////////////////////
/// TF12 default constructor
 
TF12::TF12()
{
   fCase = 0;
   fF2   = nullptr;
   fXY   = 0;
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// TF12 normal constructor.
///
/// Create a TF12 (special TF1) from a projection of a TF2
/// for a fix value `xy` of Y if option="X" or X if option="Y"
/// This value may be changed at any time via TF12::SetXY(xy)
 
TF12::TF12(const char *name, TF2 *f2, Double_t xy, Option_t *option, EAddToList addToGlobList)
      :TF1(name, "x", 0, 0, addToGlobList)
{
   SetName(name);
   fF2 = f2;
   TString opt=option;
   opt.ToLower();
   if (!f2) {
      Error("TF12","Pointer to TF2 is null");
      return;
   }
   if (opt.Contains("y")) {
      fXmin = f2->GetYmin();
      fXmax = f2->GetYmax();
      fCase = 1;
   } else {
      fXmin = f2->GetXmin();
      fXmax = f2->GetXmax();
      fCase = 0;
   }
   SetXY(xy); // has to be called after fCase is set, since it also sets the title
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// F2 default destructor.
 
TF12::~TF12()
{
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Copy constructor.
 
TF12::TF12(const TF12 &f12) : TF1(f12)
{
   f12.TF12::Copy(*this);
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Copy this F2 to a new F2.
 
void TF12::Copy(TObject &obj) const
{
   TF1::Copy(obj);
   ((TF12&)obj).fXY      = fXY;
   ((TF12&)obj).fCase    = fCase;
   ((TF12&)obj).fF2      = fF2;
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Draw a copy of this function with its current attributes.
///
/// This function MUST be used instead of Draw when you want to draw
/// the same function with different TF12 options (settings) in the same canvas.
///
/// Possible option values are:
///
/// option | description
/// -------|----------------------------------------
/// "SAME" | superimpose on top of existing picture
/// "L"    | connect all computed points with a straight line
/// "C"    | connect all computed points with a smooth curve
///
/// Note that the default value is "F". Therefore to draw on top
/// of an existing picture, specify option "SL"
///
/// Beware: this function does not clone the underlying TF2 instance,
/// it just clones the TF12 objects but the all point to the same
/// TF2. As a result, this function is only useful if you change
/// the TF12 options (settings).
/// If you want to draw projections of the same function with
/// different TF2 parameters, you can do so by previously cloning
/// the TF2 object for each variation.
/// A clone-less alternative is to create a snapshot of the TF12 by
/// creating a `new TGraph(tf12)` after each variation and then
/// adding it to a TMultiGraph.
 
TF1 *TF12::DrawCopy(Option_t *option) const
{
   TF12 *newf2 = new TF12();
   Copy(*newf2);
   newf2->AppendPad(option);
   newf2->SetBit(kCanDelete);
   return newf2;
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Evaluate this formula
///
///   Computes the value of the referenced TF2 for a fix value of X or Y
 
Double_t TF12::Eval(Double_t x, Double_t /*y*/, Double_t /*z*/, Double_t /*t*/) const
{
   if (!fF2) return 0;
   if (fCase == 0) {
      return fF2->Eval(x,fXY,0);
   } else {
      return fF2->Eval(fXY,x,0);
   }
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Evaluate this function at point x[0]
///
/// x[0] is the value along X if fCase =0, the value along Y if fCase=1
/// if params is non null, the array will be used instead of the internal TF2
/// parameters
 
Double_t TF12::EvalPar(const Double_t *x, const Double_t *params)
{
   if (!fF2) return 0;
   Double_t xx[2];
   if (fCase == 0) {
      xx[0] = x[0];
      xx[1] = fXY;
   } else {
      xx[0] = fXY;
      xx[1] = x[0];
   }
   fF2->InitArgs(xx,params);
   return fF2->EvalPar(xx,params);
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Save primitive as a C++ statement(s) on output stream out
 
void TF12::SavePrimitive(std::ostream &out, Option_t *option)
{
   thread_local Int_t save_f2_id = 9000;
 
   fF2->SavePrimitive(out, TString::Format("nodraw#%d", ++save_f2_id));
 
   TString f2Name = gInterpreter->MapCppName(TString::Format("%s%d", fF2->GetName(), save_f2_id));
 
   TString f12Name = TF1::ProvideSaveName(option);
 
   out << "   \n";
   out << "   TF12 *" << f12Name << " = new TF12(\"" << "*" << GetName() << "\", " << f2Name << ", " << fXY << ", "
       << (fCase ? "\"y\"" : "\"x\"") << ");\n";
 
   SavePrimitiveNameTitle(out, f12Name);
 
   SaveFillAttributes(out, f12Name, -1, 0);
   SaveMarkerAttributes(out, f12Name, -1, -1, -1);
   SaveLineAttributes(out, f12Name, -1, -1, -1);
 
   if (fHistogram && !strstr(option, "same")) {
      GetXaxis()->SaveAttributes(out, f12Name, "->GetXaxis()");
      GetYaxis()->SaveAttributes(out, f12Name, "->GetYaxis()");
   }
 
   SavePrimitiveDraw(out, f12Name, option);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Set the value of the constant for the TF2
///
///   constant in X when projecting along Y
///   constant in Y when projecting along X
///  The function title is set to include the value of the constant
///  The current pad is updated
 
void TF12::SetXY(Double_t xy)
{
   fXY = xy;
   if (!fF2) return;
   // option == "X" --> fCase = 0, project on X axis, X varies, Y constant 
   // option == "Y" --> fCase = 1, project on Y axis, Y varies, X constant 
   if (fCase == 0) SetTitle(TString::Format("%s (y=%g)",fF2->GetTitle(),xy));
   else            SetTitle(TString::Format("%s (x=%g)",fF2->GetTitle(),xy));
   if (fHistogram) fHistogram->SetTitle(GetTitle());
   if (gPad) gPad->Modified();
}