[R] Alter character attribute

[Phil Spector]

If you convert the dates to R date objects, I think things
will be easier:

> rawdata2$period_end_date = as.Date(rawdata2$period_end_date,format='%m/%d/%Y')
> rawdata2$mon = as.numeric(format(rawdata2$period_end_date,'%m'))
> rawdata2$year = as.numeric(format(rawdata2$period_end_date,'%Y'))

(I'm assuming you're using month/date/year.)

I can pretty much guarantee it will run in less than 18 hours :-)

 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu


On Thu, 28 Oct 2010, LCOG1 wrote:

>
> Hi everyone
>
> I have some records that include a date attribute for the date and time but
> i need to separate the data and analyze it separately in GIS by Month and
> Year, so i need to pull these attributes out and create their own attribute
> field.
>
> So the input:
> RawData2.. returns
>
>  ID   period_end_date
> 1 22 9/10/2007 0:00:00
> 2 44  2/2/2006 0:00:00
>
> and i need to get
>  ID   period_end_date    Month Year
> 22 9/10/2007 0:00:00   9         2007
> 44  2/2/2006 0:00:00    2        2006
>
> The below gets me this in list form which i can then add back into the
> initial data frame BUT
> i have over 4.5 million records and when i run the below it ran for more
> than 18 hours and only go through about 2.7 millions records when i gave up
> and ended the process.
>
> So how can i make this more efficient and possibly add the new attributes
> (month/year) to the data frame on the fly.
>
> Thanks guys....
>
> #Create sample data
> RawData2..<-data.frame(ID=c(22,44),period_end_date=c("9/10/2007
> 0:00:00","2/2/2006 0:00:00"))
>
> #Create lists to store month and year results
> Data.Month_<-list()
> Data.Year_<-list()
> #pull out year/month attribute at put in own column
> for(i in 1:length(RawData2..$ID)){
>     #Select Record
>     Data.X<-RawData..[i,]
>     #Separate date into month, day, and year
>     DateSplit<-strsplit(Data.X$period_end_date,"/")
>     #Select month
>     Month<-unlist(DateSplit)[1]
>     #Separate year from time attribute
>     Year.X<-strsplit(unlist(DateSplit)[3]," ")
>     Year.Y<-unlist(Year.X)[1]
>     Data.Month_[[i]]<-Month
>     Data.Year_[[i]]<-Year.Y
>
> }
>
>
> -- 
> View this message in context: http://r.789695.n4.nabble.com/Alter-character-attribute-tp3018202p3018202.html
> Sent from the R help mailing list archive at Nabble.com.
>
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