c f77 bootstrap.f -o bootstrap
c This program computes the uncertainty in the mean value of 15 numbers
c that do not have individual uncertainties.  The uncertainty is 
c computed via the Bootstrap Method.

      parameter (Npts=15,Ntrials=10)
      real A(Npts),A_trial(Npts),mean(Ntrials)
      integer slot(Npts)
      data A/7.1,8.3,10.5,4.0,7.7,6.3,12.8,3.3,8.2,10.0,9.2,9.3,6.6,
     :       7.0,9.6/
      idum=-479
      
      ! initialize how many times each slot is selected
      do j=1,Npts
       slot(j)=0
      enddo
      
      do n=1,Ntrials
       
       ! randomly select 15 data points
       do j=1,Npts
        n_trial=int(ran2(idum)*Npts)+1
        !if(n_trial.eq.15) print*,n_trial
        slot(n_trial)=slot(n_trial)+1
        A_trial(j)=a(n_trial)
       enddo
       
       call moment(A_trial,Npts,ave,adev,sdev,var,skew,curt)
       mean(n)=ave
             
      enddo
      
      print*
      print*
      print'(a16)','The data points:'
      print*,'7.1 8.3 10.5 4.0 7.7 6.3 12.8 3.3 8.2 10.0 9.2 9.3 6.6 ',
     :       '7.0 9.6'
      call moment(A,Npts,ave,adev,sdev,var,skew,curt)
      print 100,'have a mean of ',
     : ave,'+/-',sdev/sqrt(real(Npts-1)),
     : ', and a standard deviation of ',sdev
 100  format(a15,f4.2,a3,f4.2,a30,f4.2)
      print*
      call moment(mean,Ntrials,ave,adev,sdev,var,skew,curt)
      print'(i7,1x,a24)',Ntrials,'Bootstrap simulations:'
      print '(a16)','Average  Std_Dev'
      print '(1x,f4.2,5x,f4.2)',ave,sdev
      print*
      
      print*,'Frequency each data point is selected'
      do j=1,Npts
       print '(f4.1,1x,f5.2,a1)',A(j),
     :       slot(j)/real(Ntrials)/real(Npts)*100.,'%'
      enddo
      
      end ! of main program
      include '/usr/local/Numerical_Recipes/recipes_f/recipes/ran2.f'
      include '/usr/local/Numerical_Recipes/recipes_f/recipes/moment.f'