Something strange. The lapply only processed the first row and then wrote
that value to every row of the original dataframe. It is as if the lapply is
indeed processing every item on the list, namely each column, but the ifelse
or the as.Date is getting messed up. Not only is it only processing the
first row but it is also returning the value as numbers rather than dates. I
am now playing around with Hadley Wickham's plyr package. So far looking
good but still need to work out a few things.
Farrel Buchinsky
GrandCentral Tel: (412) 567-7870



On Wed, Dec 10, 2008 at 19:08, Marc Schwartz <marc_schwartz@comcast.net>wrote:

> Use inherits() then rather than class():
>
>  DF[] <- lapply(DF, function(x) ifelse(inherits(x, "POSIXt"),
>                                        as.Date(x), x))
>
> That should hopefully work better than my first attempt.
>
> HTH,
>
> Marc Schwartz
>
> on 12/10/2008 05:47 PM Farrel Buchinsky wrote:
> > I will try that but I am somewhat skeptical since when I go
> > class(date.of.birth) I get not just one word but two:  "POSIXt"
> > "POSIXct". Will that not mess up the logical test
> >
> > When I tried the following:
> > lapply(as.list(dataframename),class)=="POSIXt"
> > every item was false
> >
> > Farrel Buchinsky
> > GrandCentral Tel: (412) 567-7870
> >
> >
> >
> >
> >
> >> Dear Farrel,
> >> Determine the class of each column and apply as.Date() just to those
> which
> >> class is POSIX. For more details see ?class. Here is an example assuming
> >> that you're data is named "mydata":
> >> apply(mydata, 2, function(x) ifelse( class(x)=="POSIXt" |
> >>  class(x)=="POSIXlt" , as.Date(x) , x ) )
> >>
> >> HTH,
> >>
> >> Jorge
> >>
> >>
> >>
> >> On Wed, Dec 10, 2008 at 6:26 PM, Farrel Buchinsky <fjbuch@gmail.com>
> wrote:
> >>> converting a POSIX class variable to a date class is easy.
> >>> dates<-as.Date(x) #where X is of class POSIX
> >>> How does one do that to all columns in a data frame that are of POSIX
> >>> class and leave all the other columns (integers, factors) as is.
> >>>
> >>> Feel free to reply with just one or two buzzwords that I could then
> >>> search for to find how to do it.
> >>>
> >>> Farrel Buchinsky
> >>>
> >>> ______________________________________________
> >>> 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.
> >>
> >
> > ______________________________________________
> > 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.
>
>

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