replacing zeros with above/below numbers ?

HI,
May be this helps:
a1 <-a


indx <- which(c(0,diff(a!=0)) <0)
indx1 <- which(c(0,diff(a!=0)) >0)
a[a==0] <- rep( rowMeans(cbind(a[indx-1],a[indx1])),indx1-indx)
?a
# [1] 0.97210 0.97220 0.97300 0.97230 0.97145 0.97145 0.97145 0.97060 0.96980
#[10] 0.97040 0.97100 0.96990

#Another option is na.approx() from library(zoo)
?a1[a1==0] <- NA


?na.approx(a1)? ##there is difference in the result though (depends on what you want)
?[1] 0.972100 0.972200 0.973000 0.972300 0.971875 0.971450 0.971025 0.970600
?[9] 0.969800 0.970400 0.971000 0.969900
A.K.

Dear all, 

?My data is : 

a <- c(0.9721,0.9722,0.9730,0.9723,0.0,0.0,0.0,0.9706,0.9698,0.0,0.9710,0.9699) 

I want to replace zeros with ?average of before and after values
 of them. ?But sometimes there is one zero sometimes more than one. What
 is the most elegant way to do this ? 
Thanks a lot