I think this is a straightforward question but I cannot seem to find the answer. I have some mark-resighting data where most individuals (gannets) were tagged as chicks and are therefore of known age. However some were intially tagged as adults and are therefore aged 3+ at initial capture. I wanted to set up a model where the age-specific survival part is: for (i in 1:udot) { for (j in first[i]:(k-1)){ S[i,j]<-s.age[age[i]+j-first[i]+1] }} for (y in 1:30){ s.age[y]~dbeta(1,1) } k is last sampling period, udot is number of individuals, first[i] is the sampling period at initial capture. However age[i] is mostly 0, but not known for some, i.e. in the data age[i]=c(0,0,0,0,NA,0,0,0... etc) I tried something like: age[i]~dgamma(3,0.5) age.use<-round(age[i]) and then modelled: S[i,j]<-s.age[age.use[i]+j-first[i]+1] But I get the message that age.use[1] is not data. Also, I would like to truncate the imputed ages at a minimum of 3, and a maximum of about 15.... Many thanks Andrew ------------------------------------------------------------------- This list is for discussion of modelling issues and the BUGS software. For help with crashes and error messages, first mail [log in to unmask] To mail the BUGS list, mail to [log in to unmask] Before mailing, please check the archive at www.jiscmail.ac.uk/lists/bugs.html Please do not mail attachments to the list. To leave the BUGS list, send LEAVE BUGS to [log in to unmask] If this fails, mail [log in to unmask], NOT the whole list