c2--567--1---------2---------3---------4---------5---------6---------712
      Subroutine linear_fit(x, y, a, b, n)
c
c     -- Linear_fit/Linear fit of a set of points/N. Nath/May '01
c
c     -- Function:  Given x(i), y(i) for i = 1 through n, this routine
c        finds the best fit for y(i) to a*x(i) + b.
c
            implicit none
c
c     -- Input & Output Variables:
c
            real        x(n), y(n)
                              !abscissa & ordinate (input)

            real        a, b  !slope & intercept (output)

            integer     n     !number of data points (input)

c
c     -- Local Variables:
c
            real        c11, c12, c22, d1, d2, det

            integer     i
c
      c11 = 0.0
      c12 = 0.0
      do i = 1,n
         c11 = c11 + x(i)**2
         c12 = c12 + x(i)
      end do
      c22 = n

      d1 = 0.0
      d2 = 0.0
      do i = 1,n
         d1 = d1 + x(i)*y(i)
         d2 = d2 + y(i)
      end do

      det = c11*c22 - c12**2
      a = (c22*d1 - c12*d2)/det
      b = (-c12*d1 + c11*d2)/det
c
      return
      end