Both ROOT and Geant4 are C++ libraries you can link to. You don't integrate ROOT to Geant4 or vice versa. You write your own C++ code using functions provided in ROOT and Geant4 libraries. As a start, you can learn how to write a stand-alone C++ program using ROOT libraries by following examples in ROOT tutorials. You can also learn how to write a stand-alone C++ program using Geant4 libraries by following simple Geant4 examples. Once you are confident with both, you are able to link both libraries in your stand-alone C++ program.

Of course ROOT is very powerful. Nevertheless, I prefer to produce (even large) selective ASCII outputs and treat these through GNU octave or matlab. ROOT needs time so that a user is efficient.

I agree with Dimitrios and consider it simpler to use my own histogram library, write my own output and the process the results in Matlab. Which says more about my limitations than about Root :-)

What do you mean by your second question? Are you able to build the examples or are you not able to build them?

Dear Patrik

It's my mistake instead of 'unable' I wrote 'able'.

After building that example when I execute the any mac file,it automatically closing that OpenGL window. 

you just install root  in your computer and use there library  in your Geant4 code that will work . And don't forget to shared your root library using bash scripting (thisroot.sh) if you are working in shell environment .

@Jay

can you tell how i add the root library to Geant4 code, or this can be done by simply coping all the lib of root to geant4 lib.

I am sharing root library using bash scripting (thisroot.sh).

@Gopalji ,

Ok , Sounds good , you are doing good . You don't have to copy root library in your Geant4 library . you just start writing your Geant4 codes and use the roots classes in your codes . All the things will work .

@Jaydip

I try one basic example in which root library are used but it is not being build , means during build its asking TH1D.hh, i copied that .hh file of root to the include folder of that example, it doesn't worked.

There are Geant4 examples in which root files are generated. You can them browse them using ROOT.

Alternatively, you can simply generate data output from Geant4, and then do the analysis using ROOT.

@Saed

that i did but some of the example required Root header file for there build, in that case what should i do.

you can also ask the experts on forum  http://hypernews.slac.stanford.edu/HyperNews/geant4/cindex

in Interface-Analiysis category.