subroutine myfcn(npar, g, f, x, iflag, futil)
C
      implicit none
      integer npar, iflag, i, ndat
      integer SYSIN/1/, SYSRD/5/, SYSWR/6/, SYSPU/7/
      parameter (ndat=5)
C
      real*8 f, g(*), x(*), xdat(ndat), ydat(ndat), edat(ndat), func,        
     >       answer/15.7/, rms, avg, diff
C
C     Save all data that must be preserved between calls!
C
      save xdat, ydat, edat
C
      external futil
C
      if (iflag .eq. 1) then
C
C     Initialization mode
C
         do i=1,ndat
            xdat(i) = i
            ydat(i) = answer + i - float(ndat + 1) / 2.
            edat(i) = 1.
         end do
      end if
C
C     compute LSQ
C
      f = 0
      do i = 1, ndat
         f = f + (ydat(i) - func(xdat(i), x(1)))**2 / edat(i)
      end do
      if (iflag .eq. 3) then
C
C     print mode
C
         avg = 0
         rms = 0
         write(SYSWR, '(''    X       Y      dY      func    pull'')')
         do i = 1, ndat
            diff = (ydat(i) - func(xdat(i), x(1))) / sqrt(edat(i))
            avg = avg + diff
            rms = rms + diff**2
            write(SYSWR, '(10f8.3)') xdat(i), ydat(i), edat(i),
     >                               func(xdat(i), x), diff
         end do
         avg = avg / ndat
         rms = rms / ndat - avg**2
         write(SYSWR, '('' mean pull'', f10.3, '' rms of pulls :'',
     >         2f10.4)') avg, rms
         write(SYSWR, *) ' '
      end if
      end