program cfit1
c
c -- linear least-squares fit
c -- figure 5.1
c     
      integer length, out, max
      real x(20), y(20)
      common /inout/ out, max
c
      out = 6
      max = 20
10    call input(x, y, length)
      call output(x, y, length)
      goto 10
      end
      subroutine input(x, y, n)
c -- get values for n and arrays x and y
c
      integer n, out, i, j, max
      real x(n), y(n), fudge
      common /inout/ out, max
      data a/2.0/, b/5.0/
c
      write(out, 101)
      read(*,103) fudge
      if (fudge .lt. 0.0) goto 99
5     write(out, 102)
      read(*,104) n
      if (n .gt. max) goto 5
      if (n .lt. 0) goto 99
      do 10 i = 1, n
       j = n + 1 - i
       x(i) = j
       y(i) = (a + b*j)*(1.0+(2.0*rand(0) - 1.0)*fudge)
10    continue
      return
99    stop
101   format(/' fudge? ' )
102   format(' how many points? ' )
103   format(f10.0)
104   format(i2)
      end
      subroutine output(x, y, n)
c
c -- print out the answers
c
      integer n, out, i
      real x(n), y(n)
      common /inout/ out, max
c
      write(out, 101)
      write(out, 102) (i, x(i), y(i), i = 1, n)
      return
101   format('   i      x       y')
102   format(i4, f8.1, f9.2)
      end