I recommend not putting POSIXlt vectors in data frames because of memory use
and added complexity of the resulting data frame. That is, use
colClasses = c('character', 'POSIXct', 'POSIXct')
instead. The POSIXlt values will still be created as temporary variables for
reading in, but the data frame will store only the simpler and more compact
type for later use.
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Sent from my phone. Please excuse my brevity.
David Winsemius <dwinsem...@comcast.net> wrote:
>
>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
>
>______________________________________________
>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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