ddply - how to transform df column "in place"
Hi Jean,
On Tue, Aug 23, 2011 at 6:16 PM, jjap <jean.plamondon at fpinnovations.ca> wrote:
Dear R-users,
I am trying to get the plyr syntax right, without much success.
Given:
d<- data.frame(cbind(x=1,y=seq(20100801,20100830,1)))
names(d)<-c("first", "daterep")
d2<-d
# I can convert the daterep column in place the classic way:
d$daterep<-as.Date(strptime(d$daterep, format="%Y%m%d"))
# How to do it the plyr way?
ddply(d2, c("daterep"), function(df){as.Date(df, format="%Y%m%d")})
# returns: Error in as.Date.default(df, format = "%Y%m%d") :
# ? do not know how to convert 'df' to class "Date"
There is no "plyr way" to do this, as this is not the kind of operation plyr is designed to carry out. plyr is designed to simplify the process of 1) splitting the data into groups, 2) operating on each group, and 3) putting the results back together. Since your example does not involve this kind of split-apply-combine approach plyr will not help you. HTH, Ista
Thanks for any hints, ---jean -- View this message in context: http://r.789695.n4.nabble.com/ddply-how-to-transform-df-column-in-place-tp3764037p3764037.html Sent from the R help mailing list archive at Nabble.com.
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Ista Zahn Graduate student University of Rochester Department of Clinical and Social Psychology http://yourpsyche.org