First thing to notice in your second example is that you have "factor" for what you think are strings. You should try:
u2<-as.difftime(c(as.character(a),as.character(b)), format ="%Y-%m-%d %H:%M:%S", units="mins") and see if this gives you what you are expecting. If you are reading this in with 'read.table', you might want to specify those columns as characters, or use 'as.is=TRUE' to prevent conversion to factors. If you are not using factors, then you probably want the character strings. On Mon, Apr 5, 2010 at 9:19 AM, steve012 <stephenadr...@gmail.com> wrote: > > I'm new to R and have the following problem with difftime: > > if I directly assign date/time strings in difftime I get the expected > result: > > > a<-"2010-03-23 10:52:00" > > a > [1] "2010-03-23 10:52:00" > > b<-"2010-03-23 11:53:00" > > u2<-as.difftime(c(a,b), format ="%Y-%m-%d %H:%M:%S", units="mins") > > u2 > Time differences in mins > [1] -18008 -17947 > attr(,"tzone") > > > However, if I first assign the values of "a" and "b" from a data frame > within a loop I get a different result: > > a<-u[i] > > a > [1] 2010-03-23 10:52:00 > 6838 Levels: 2010-03-18 16:54:00 2010-03-18 16:55:00 ... 2010-03-23 > 11:53:00 > b<-u[i+1] > > b > [1] 2010-03-23 11:53:00 > 6838 Levels: 2010-03-18 16:54:00 2010-03-18 16:55:00 ... 2010-03-23 > 11:53:00 > u2<-as.difftime(c(a,b), format ="%Y-%m-%d %H:%M:%S", units="mins") > > u2 > Time differences in mins > [1] 6837 6838 > > > So, how do use difftime in the context of a loop? Thanks. > -- > View this message in context: > http://n4.nabble.com/using-difftime-tp1751607p1751607.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html> > and provide commented, minimal, self-contained, reproducible code. > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve? [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
