#include "TStyle.h"
#include "TCanvas.h"
#include "TF2.h"
#include "TTimer.h"   
#include "TMath.h"
#include "TAxis.h"
#include "TROOT.h"
#include "TSystem.h"
#include "Math/SpecFunc.h"
#include <iostream>
#include <sstream>
#include <iomanip>

Double_t myf(Double_t *x, Double_t *par) {
  Double_t xx = x[0];
  Double_t yy = x[1];
  Double_t rr = sqrt(xx*xx+yy*yy);
  Double_t costh = xx/rr;
  Double_t sum = 0;
  Int_t lmax = (Int_t)par[0];

  for (Int_t l=0; l <= lmax; l++) {
    if(l%2==0){
      sum += TMath::Power(-1,l/2.)*(2*l+1)*
	ROOT::Math::sph_bessel(l,rr)*
	ROOT::Math::legendre(l,costh);
    }
  }
  return sum;
}

void plot()
{
  gROOT->SetStyle("Plain");
  gStyle->SetTitleAlign(23);
  gStyle->SetTitleX(0.54);
  gStyle->SetTitleY(0.97);
  gStyle->SetTitleBorderSize(0);
  gStyle->SetTitleFillColor(0);
  gStyle->SetTitleColor(1);
  gStyle->SetLabelFont(132,"xyz");
  gStyle->SetTitleFont(132,"xyz");
  gStyle->SetTitleFont(132,"");
  gStyle->SetTextFont(132);
  gStyle->SetStatFont(132);
  gStyle->SetNdivisions(505,"xyz");
  gStyle->SetLabelSize(0.075,"xyz");
  gStyle->SetTitleSize(0.075,"xyz");
  gStyle->SetTitleSize(0.06,"");
  gStyle->SetPadTopMargin(0.2);
  gStyle->SetPadRightMargin(0.10);
  gStyle->SetPadLeftMargin(0.20);
  gStyle->SetPadBottomMargin(0.18);
  
  TCanvas *c1 = new TCanvas("c1","c1",400,400);
  TF2 *f = new TF2("f",myf,-19.999,20,-20,20,1);
  f->SetNpx(50);
  f->SetNpy(50);
  f->SetMaximum(2);
  f->SetMinimum(-1.999);
  for (Int_t i =0; i < 33;i++){
    f->SetParameter(0,i);
    f->GetXaxis()->SetTitle("#it{x}");
    f->GetYaxis()->SetTitle("#it{y}");
    {
      std::ostringstream os;
      os << "Re#[]{ #Sigma_{#it{l}=0}^{" << i << "} #it{i}^{#it{l}} (2#it{l}+1) #it{j}_{#it{l}}(#it{r})#it{P}_{#it{l}}(cos#theta)}";
      f->SetTitle(os.str().c_str());
    }
    f->Draw("surf1");
    {
      std::ostringstream os;
      os << "fig" <<std::setw(2) << std::setfill('0')<<  i << ".gif";
      c1->Print(os.str().c_str());
    }
  }
}