[R] How to combine character month and year columns into one column

[David Winsemius]

Marc;

Feature request:

Would it make sense to construct month.abb as a named vector so that the operation that was attempted would have succeeded? Adding alphanumeric names c("01", "02", "03", "04", "05", "06",
"07", "08", "09", "10", "11", "12") would allow character extraction from substring or regex extracted month values which are always character-class.

Example:

> names(month.abb) <- c("01", "02", "03", "04", "05", "06",
+ "07", "08", "09", "10", "11", "12")
> month.abb
   01    02    03    04    05    06    07    08    09    10    11    12 
"Jan" "Feb" "Mar" "Apr" "May" "Jun" "Jul" "Aug" "Sep" "Oct" "Nov" "Dec" 


> month.abb[ substr(Sys.Date(), 6,7) ]
   09 
"Sep" 

-- 
David.

On Sep 23, 2014, at 9:03 AM, Marc Schwartz wrote:

> On Sep 23, 2014, at 10:41 AM, Kuma Raj <pollaroid at gmail.com> wrote:
> 
>> Dear R users,
>> 
>> I have a data with  month and year columns which are both characters
>> and wanted to create a new column like Jan-1999
>> with the following code. The result is all NA for the month part. What
>> is wrong with the and what is the right way to combine the two?
>> 
>> ddf$MonthDay <- paste(month.abb[ddf$month], ddf$Year, sep="-" )
>> 
>> 
>> Thanks
>> 
>>> dput(ddf)
>> structure(list(month = c("01", "02", "03", "04", "05", "06",
>> "07", "08", "09", "10", "11", "12"), Year = c("1999", "1999",
>> "1999", "1999", "1999", "1999", "1999", "1999", "1999", "1999",
>> "1999", "1999"), views = c(42, 49, 44, 38, 37, 35, 38, 39, 38,
>> 39, 38, 46), MonthDay = c("NA-1999", "NA-1999", "NA-1999", "NA-1999",
>> "NA-1999", "NA-1999", "NA-1999", "NA-1999", "NA-1999", "NA-1999",
>> "NA-1999", "NA-1999")), .Names = c("month", "Year", "views",
>> "MonthDay"), row.names = 109:120, class = "data.frame")
>>> 
>> 
> 
> 
> 
> Since you are trying to use ddf$month as an index into month.abb, you will either need to coerce ddf$month to numeric in your code, or adjust how the data frame is created.
> 
> In the case of the former approach:
> 
>> paste(month.abb[as.numeric(ddf$month)], ddf$Year, sep="-" )
> [1] "Jan-1999" "Feb-1999" "Mar-1999" "Apr-1999" "May-1999" "Jun-1999"
> [7] "Jul-1999" "Aug-1999" "Sep-1999" "Oct-1999" "Nov-1999" "Dec-1999"
> 
> 
> Regards,
> 
> Marc Schwartz
> 
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David Winsemius
Alameda, CA, USA