Construct a TF2 with two TF1s

ROOT
1

Hello,

first, thank you all for this forum, I often find here the solution of my problems and it gives me a great help.

As in subject, I would like to construct a TF2 object with two TF1s, something like this:

TF1 *f1 = new TF1("f1", "some function f1...", x1min, x1max);
TF1 *f2 = new TF1("f2", "some function f2...", x2min, x2max);

TF2 *f = new TF2("f", "f1(x) * f2(y)", x1min, x1max, x2min, x2max);

It would be better if the TF2 doesn’t have to know what functions are f1 and f2.
I looked for a constructor with TF1s in the TF2 page, but I didn’t find anything.

Is there a way to do this?
Thank you in advance,
Antonio.

2

see attached file.
f1f2.C (177 Bytes)

3

Thank you for your quick reply.

This solution is simple and clear, but awfully it doesn’t work in my environment. Could it be because I’m using it inside a class? Explaining in detail, I have just written the following code:

From ‘Likeratio.cc’:

double Likeratio::f1(double x){
  return x + 2;
}

double Likeratio::f2(double x){
 return x + 3;
}

TF2* Likeratio::prova(){
  TF2*f2d = new TF2("f2d", "this->f1(x) * this->f2(y)",-5,15,-5,15);
  return f2d;
}

From main.cpp:

TF2* prova = l.prova();
cout<<prova->GetXmin()<<endl;

I don’t get any error when compiling, but when I start a run it gives the following error:

Error in TFormula::Compile: Bad numerical expression : "this.f1(x)"
Error in TF2::TF2: function: f2d/this->f1(x) * this->f2(y) has 0 parameters instead of 2

I tried also writing f1(x), instead of this->f1(x), but the outcome is the same.

Best regards,
Antonio

4

does it work if you do not write f1 and f2 inside the class ?

5

No, unfortunately it doesn’t, but I think I have just understood the reason. The problem is I use a Makefile to compile:

[code]
ROOTCFLAGS = $(shell /usr/bin/root-config --cflags)
ROOTLIBS = $(shell /usr/bin/root-config --libs)
ROOTGLIBS = $(shell /usr/bin/root-config --glibs)
OTHERLIBS = -lMinuit # -lRooFitCore -lFoam

CXX = g++
CXXFLAGS = -g $(ROOTCFLAGS)
DEPEND = $(CXX) -MM
DEL = rm -rf

LD = g++
LDFLAGS = -O4 $(ROOTLIBS) $(OTHERLIBS)

SOURCES := $(wildcard *.cc)
OBJECTS := $(SOURCES:.cc=.o)
EXESRC := $(wildcard *.cpp)
EXECUTABLES := $(EXESRC:.cpp=.exe)

all: $(EXECUTABLES)

%.exe : %.cpp $(OBJECTS); ${LD} $(CXXFLAGS) $< $(OBJECTS) $(LDFLAGS) -o $@

%.o : %.cc; $(CXX) $(CXXFLAGS) -c $< -o $@

%.d : %.cc; $(DEPEND) $(CXXFLAGS) $< > $@

%.d : %.cpp; $(DEPEND) $(CXXFLAGS) $< > $@; sed s/.o:/.exe:/g $@ > tmp.sed; mv tmp.sed $@

clean: ; $(DEL) *.d; $(DEL) *.o; $(DEL) *.exe

#include $(SOURCES:.cc=.d)
#include $(EXESRC:.cpp=.d)[/code]

In fact, even with the macro you sent me, it works with the command ‘root -l f1f2.C’, but not with the Makefile (launching main.exe gives the same error of a bad numerical expression). I can’t imagine a solution for this problem, because I need the Makefile to link all my classes.

Thank you anyway.
Best regards,
Antonio

6

The macro I sent you should work also in compile mode. What is the exact error message you get ?