R help - Apr 2012 - Can I specify POSIX[cl]t column classes inside read.csv?

I'm loading a nicely formatted csv file.

? ? #!/usr/bin/env Rscript
? ? kpi <- read.csv(
? ? ? # This is a dump of the username, date_joined and last_login columns
? ? ? # from the auth_user Django table.
? ? ? 'data/2012-04-23.csv',
? ? ? colClasses = c('character')
? ? )
? ? print(kpi[sample(nrow(kpi), 3),2:3])

Here's what the three rows I printed look like.

? ? ? ? ? ? ?last_login ? ? ? ? date_joined
? ? 2012-02-22 02:44:11 2011-09-19 03:07:35
? ? 2011-09-16 01:34:41 2011-09-16 01:34:41
? ? 2011-07-02 20:29:17 2011-07-02 20:29:17

Once I load them, I'm converting the datetimes to datetimes.

? ? kpi$last_login <- as.POSIXlt(kpi$last_login)
? ? kpi$date_joined <- as.POSIXlt(kpi$date_joined)

Can I do this inside of read.csv by specifying colClasses? It's
obviously not a problem if I can't; it just seems like I should be
able to.

Note that the following doesn't work because it doesn't save the times.

? ? colClasses = c('character', 'Date', 'Date')

Thanks

Tom

On Apr 23, 2012, at 11:48 AM, Thomas Levine wrote:
> I'm loading a nicely formatted csv file.
>
>     #!/usr/bin/env Rscript
>     kpi <- read.csv(
>       # This is a dump of the username, date_joined and last_login  
> columns
>       # from the auth_user Django table.
>       'data/2012-04-23.csv',
>       colClasses = c('character')
>     )
>     print(kpi[sample(nrow(kpi), 3),2:3])
>
> Here's what the three rows I printed look like.
>
>              last_login         date_joined
>     2012-02-22 02:44:11 2011-09-19 03:07:35
>     2011-09-16 01:34:41 2011-09-16 01:34:41
>     2011-07-02 20:29:17 2011-07-02 20:29:17
>
> Once I load them, I'm converting the datetimes to datetimes.
>
>     kpi$last_login <- as.POSIXlt(kpi$last_login)
>     kpi$date_joined <- as.POSIXlt(kpi$date_joined)
>
> Can I do this inside of read.csv by specifying colClasses?

Possibly. If there is an "as" function for a particular class, it can
be used in the colClasses vector of read.* functions. It appears that  
your input file might have the right combination of formats and  
separators for this to succeed.


> It's
> obviously not a problem if I can't; it just seems like I should be
> able to.
>
> Note that the following doesn't work because it doesn't save the  
> times.
>
>     colClasses = c('character', 'Date', 'Date')

Try instead:

colClasses = c('character', 'POSIXlt', 'POSIXlt')


-- 

David Winsemius, MD
West Hartford, CT