subroutine intrr1(rdat,n)
c
c interpolates missing (.lt.0) values in real count array rdat(n)
c will allow up to 3 contiguous non-defined values, more than three and
c interpolation is inhibited.
c
c v1.0 jfe johnson 15 nov 81
c
	real rdat(n)
	real factj(2,2),factk(2,2)
	data factj/0.5,0.333,0.667,0.5/
	data factk/0.5,0.667,0.333,0.5/
c
	do 10 i=1,n
c is this value defined ?
	if(rdat(i).ge.0.0)go to 10
c no, so look at left side
	if(i.le.1)go to 10
	j=i-1
	if(rdat(j).ge.0.0)go to 20
	if(j.le.1)go to 10
	j=j-1
	if(rdat(j).ge.0.0)go to 30
	go to 10
   20	il=1
	go to 40
   30	il=2
   40	continue
c now look at right side
	if(i.ge.n)go to 10
	k=i+1
	if(rdat(k).ge.0.0)go to 50
	if(k.ge.n)go to 10
	k=k+1
	if(rdat(k).ge.0.0)go to 60
	go to 10
   50	ir=1
	go to 70
   60	ir=2
   70	continue
c appropriate combination defined - so interpolate
	rdat(i)=factj(il,ir)*rdat(j)+factk(il,ir)*rdat(k)
   10	continue
	return
	end