how to convert yearmon to numbers indicating the order of date

Question

I have a column that looks like this:

enter image description here

I want to create another column that indicates 'April 2018' is '1', 'May 2018' is '2'. I tried to use rank(), but I only got this:

data$'X1'<-rank(as.numeric(as.Date(data$MONTH)))

enter image description here

Answer 1

Package lubridate has a lot of convenience functions for handling dates. In your case:

library(lubridate)
the_date  <- 'April 2018'
paste(the_date, 'is month number',
      month(my(the_date))
      )

Note that the function name my is short for month and year, following lubridate's mnemonic function naming.