//histogram 
#define ndata 1000 //pocet dat
#define nbins 100 //pocet binu
int run()
{
        FILE *fin,*fout; //soubor odkud se prectou a kam se zapisi data
        double x[ndata];
        double x_min,x_max;   //minimalni a maximalni hodnota - meze histogramu 
        fin=fopen("data.dat","r"); //vstupni soubor s daty
        fout=fopen("histogram.txt","w"); //vstupni soubor s daty
        for (int i = 0; i < ndata; ++i) 
        {
          fscanf(fin,"%lf",&x[i]);     //nacte data
          if(i==0) x_min=x_max=x[i];   //aby nebyly nedefinovane
          if(x[i]<x_min) x_min=x[i];
          if(x[i]>x_max) x_max=x[i];
        }
        fclose(fin);
        printf("min value: %lf\n",x_min);
        printf("max value: %lf\n",x_max);
        printf("bin width: %lf\n",(x_max-x_min)/nbins);
        TH1D *hist = new TH1D("hist", "histogram", nbins, x_min, x_max);
        for (int i = 0; i < ndata; ++i) hist->Fill(x[i]);  //naplneni histogramu
        TCanvas *c1 = new TCanvas("c1", "histogram",5,5,800,600); //definice okna
        hist->Draw();     //nakresli histogram
        for (int i = 0; i < nbins; ++i) //zapis histogramu do souboru fout
        {
          counts=hist->GetBinContent(i);  //zjisteni hodnoty v i-tem binu
          fprintf(fout,"%lf %ld\n",i*(x_max-x_min)/nbins+x_min,counts);
        }
          fclose(fout);
        return(0);
}