subroutine interp(nk_ti,nu_ti,k_ti,nu,kf,k)
      implicit none
      include 'max.inc'
      integer nk_ti,i,kf
      double precision nu_ti(1:Npmx)
      double precision k_ti(1:Npmx)
      double precision nu,k
      
      do i=1,nk_ti
         if (nu_ti(i).eq.nu) then
            k=k_ti(i)
            kf=1
            goto 666
         endif
         if (nu_ti(i).gt.nu) then
            goto 111
         endif
      enddo
      if (nu.gt.nu_ti(nk_ti)) then
         kf=0
         goto 666
      endif
 111  continue
      if (i.gt.1) then
         k=k_ti(i-1)+(k_ti(i)-k_ti(i-1))/(nu_ti(i)-nu_ti(i-1))
     &        *(nu-nu_ti(i-1))
         kf=1
      else
         write(*,*) 'Error from routine interp:'
         write(*,*) 'i=',i
         stop
      endif

 666  continue
      return
      end