c c c
      subroutine linint(x,y)
c
c     Given a value of x return a value of y based on interpolation
c     within a table of y values (ytab) corresponding to the x values
c     contained in the array xtab.  The subroutine assumes that the
c     values in xtab increase monotonically.  Efficiency is increased
c     by remembering the table points used in the last call (ilast).
c
c    John Mahaffy 2/12/95
c
      real xtab(11),ytab(11)
c
      save ilast
c
      data ytab/1.0,2.1,3.2,4.4,5.7,7.1,8.6,10.2,11.9,13.7,15.8/
      data xtab
     & /300.,400.,500.,600.,700.,800.,900.,1000.,1100.,1200.,1300./
      data ilast/1/
      if (x.le.xtab(ilast+1)) then
          do 20 i1=ilast,1,-1
              if(x.ge.xtab(i1)) go to 60
  20          continue
          write(6,*) 'x = ', x, '  is below the table range'  
          stop
      else
          do 40 i1=ilast+1,10
              if(x.le.xtab(i1+1)) go to 60
  40          continue
          write(6,*) 'x = ', x, '  is below the table range'  
          stop
      endif
  60  wx=(x-xtab(i1))/(xtab(i1+1)-xtab(i1))
      y=(1-wx)*ytab(i1)+wx*ytab(i1+1)
      ilast=i1
      return
      end
c
c c