[R] Check Dates

[Wang, Kevin (SYD)]

Hi,

I'm trying to check a column of dates and creating indicator variables showing different time periods.

For example, if I were to do this in Excel I would have something like:
   Year to Dec 2004=IF(AND(referral date<DATE(2005,1,1), OR($closure date>DATE(2003,12,31), LEN($closure date) = 0)), "Yes", "No")
for the "Year to Dec 2004" column.

I've read the data into R and converted the two columns (referral date and closure date) to as.Date() format (found this format from r-help):
referral <- as.Date(issues.sub$Referraldate, "%d/%m/%Y")
closure <- as.Date(issues.sub$Dateofclosure, "%d/%m/%Y")

But then have trouble doing the "if" checking.  I tried something like:
Dec04<- ifelse(referral < as.Date("1/1/2005", "%d/%m/%Y") & 
               (closure > as.Date("31/12/2003", "%d/%m/%Y") || closure = ""), "Yes", "No")

but got an error message:
Error in closure > as.Date("31/12/2003", "%d/%m/%Y") || closure = "" : 
  could not find function "||<-"

I haven't really played with dates in R before so would really appreciate some guidance on this.

(I'm avoiding Excel because there are over 130,000 rows to check, and I need to repeat this process for each quarter since Dec 2004.  When I tried this in Excel it just took all the memory I have on my computer and freezes the entire workbook).

Cheers
Kevin


Kevin Wang 
Senior Advisor, Health and Human Services Practice 
Government Advisory Services

KPMG 
10 Shelley Street 
Sydney  NSW  2000  Australia

Tel     +61 2 9335 8282 
Fax     +61 2 9335 7001

kevinwang at kpmg.com.au





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