Conditional creation of Variable using R

Question

I'm trying to create a new var "PERIOD" based on dates. The sample data is given below:

Date
1/10/2012
1/11/2012
1/12/2012
1/13/2012
1/14/2012
1/15/2012
1/16/2012
1/17/2012
1/18/2012

After conditioning the new dataset looks like:

  Date      PERIOD
1/10/2012     Y1
1/11/2012     Y1
1/12/2012     Y1
1/13/2012     Y1
1/14/2012     Y1
1/15/2012     Y2
1/16/2012     Y2
1/17/2012     Y2
1/18/2012     Y2

The code I was using is

dat$PERIOD<-{If '1/10/2012' <=  as.Date(dat$Date) <= '1/14/2012' dat$PERIOD='Y1' else
    If '1/15/2012' <=  as.Date(dat$Date) <= '1/18/2012'dat$PERIOD='Y2'
}

But I'm getting error:

Error: unexpected string constant in dat$PERIOD<-{If '1/10/2012'

Thank you. Regards,

sgibb · Accepted Answer · 2012-10-14 08:27:33Z

2

Please see ?as.Date for correct date format.
Your conditional statement is mostly wrong. R is case sensitive. You have to use if. Please find some example code below:

d <- data.frame(Date=as.Date(paste(2012, 1, 10:18, sep="/")), stringsAsFactors=FALSE)
d$PERIOD <- ifelse(as.Date("2012/1/15") > d$Date, "Y1", "Y2")

answered Oct 14, 2012 at 8:27

sgibb

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