R help - Dec 2008 - converting multiple columns from POSIX* to Date

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

on 12/10/2008 05:26 PM Farrel Buchinsky 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
If 'DF' is your source data frame, something like:

  DF[] <- lapply(DF, function(x) ifelse(class(x) == "POSIXt",
                                        as.Date(x), x)


This is untested, so proceed with due caution.

HTH,

Marc Schwartz

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 at
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
>>
>> ______________________________________________
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>> 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.
>
>