subroutine splset(x,y,c,m)
c***********************************************************************
c
c        this subroutine was taken from_
c             introductory computer methods and numerical analysisby
c                  ralph h. pennington
c        the mcmillan company -newyork 1965.
c        this subroutine will accept up to 487 points.
c
c***** x = independent variable
c***** y = dependent variable
c***** m = number of data points in the x and y arrays
c***** c = coefficents of the cubic that is fit between adjacent data po
c***** the following dimensions must be .ge. m
c***********************************************************************
      implicit integer*4(i-n),real*8 (a-h,o-z)
      real*8 d(487), p(487), e(487), a(487,3), b(487), z(487)
      real*8 x(1),y(1),c(4,1)
      mm=m-1
      do 2 k=1,mm
      d(k)=x(k+1)-x(k)
      p(k)=d(k)/6.
  2   e(k)=(y(k+1)-y(k))/d(k)
      do 3 k=2,mm
  3   b(k)=e(k)-e(k-1)
      a(1,2)=-1.-d(1)/d(2)
      a(1,3)=d(1)/d(2)
      a(2,3)=p(2)-p(1)*a(1,3)
      a(2,2)=2.*(p(1)+p(2))-p(1)*a(1,2)
      a(2,3)=a(2,3)/a(2,2)
      b(2)=b(2)/a(2,2)
      do 4  k=3,mm
      a(k,2)=2.*(p(k-1)+p(k))-p(k-1)*a(k-1,3)
      b(k)=b(k)-p(k-1)*b(k-1)
      a(k,3)=p(k)/a(k,2)
  4   b(k)=b(k)/a(k,2)
      q=d(m-2)/d(m-1)
      a(m,1)=1.+q+a(m-2,3)
      a(m,2)=-q-a(m,1)*a(m-1,3)
      b(m)=b(m-2)-a(m,1)*b(m-1)
      z(m)=b(m)/a(m,2)
      mn=m-2
      do 6 i=1,mn
      k=m-i
  6   z(k)=b(k)-a(k,3)*z(k+1)
      z(1)=-a(1,2)*z(2)-a(1,3)*z(3)
      do 7 k=1,mm
      q=1./(6.*d(k))
      c(1,k)=z(k)*q
      c(2,k)=z(k+1)*q
      c(3,k)=y(k)/d(k)-z(k)*p(k)
  7   c(4,k)=y(k+1)/d(k)-z(k+1)*p(k)
      return
      end