[R-sig-ME] Help!

[Eric ADJAKOSSA]

Hello dear friends.
 My name is Eric H. Adjakossa. I am a
student in master of statistics in Benin (West Africa). I am about to
use the book "Mixed-effects models in S and S-plus" as part of my
master's thesis. I adjusted a linear mixed effects model, but I can
not make some graphs to validate this model. I use the software R
(version 2.13.0). In fact R displays errors that I can not correct for
several days. I thought call you for help. I will be very happy to get
your help. Here are the codes and the error that R displays:

groupCSP <- groupedData(conCSP ~ NBDORM_f | VILLAG, data =
subset(Tori_util_sd, select = c(conCSP,TOTTDR_f, TOTTDR, VILLAG
,IND_VEGET_f , NBDORM_f, EAU, TMUR, NO, LONG, LAT)))


cm <- lme(log(conCSP) ~ NBDORM_f + EAU*IND_VEGET_f + TOTTDR , data =
groupCSP, random = ~ 1 | VILLAG, na.action = na.omit)


> plot( cm, VILLAG~resid(.), abline = 0 )
Erreur dans `[<-.data.frame`(`*tmp*`, , ".y", value = c(2L, 2L, 2L, 2L, 8L,  :
 replacement has 479 rows, data has 481

I hope very much your answer. Thank you very much in advance.