Hello,
Try
#
# Adapted from several posts to R-Help,
# mostly by David Winsemius, also by Gabor Grothendiek.
#
nweek <- function(x, format="%Y-%m-%d", origin){
if(missing(origin)){
as.integer(format(strptime(x, format=format), "%W"))
}else{
x <- as.Date(x, format=format)
o <- as.Date(origin, format=format)
w <- as.integer(format(strptime(x, format=format), "%w"))
2 + as.integer(x - o - w) %/% 7
}
}
dates<- as.Date(c("1996-03-29","1996-05-30","1996-09-28","1996-05-09"))
nweek(dates)
nweek(dates, origin="1995-12-30")
Note that you have used two different date formats, Y-m-d (dates vector) and
Y-d-m (origin).
Above the origin is consistent with the rest.
Hope this helps,
Rui Barradas
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