For loop help (R) - r

Question

I would like to have a for loop for this:
months = c("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December")
years = c(2018, 2019)
input = 17
for (i in 1:input) {
output[i] = paste(months[i], years[i], sep = " ")????
NEED HELP HERE. rep() ???
}
And I would like the output to be a vector that consists on 17 months:
Output = c("January 2018", "February 2018", "March 2018", "April 2018", ... , "May 2019")
Thank you very much for your help.

Answer 1

Another option will be this:
> c(outer(month.name, 2018:2019, paste))[1:17]
[1] "January 2018" "February 2018" "March 2018"
[4] "April 2018" "May 2018" "June 2018"
[7] "July 2018" "August 2018" "September 2018"
[10] "October 2018" "November 2018" "December 2018"
[13] "January 2019" "February 2019" "March 2019"
[16] "April 2019" "May 2019"

Answer 2

There's already a system supplied vector of month names: month.name. Since paste is vectorized and does recycling, there's no need for a for loop and the default separator for paste is " ", so the code could just be:
output <- paste( month.name, rep( years, each=12) )[1:17]
# test result ----
> output
[1] "January 2018" "February 2018" "March 2018" "April 2018" "May 2018" "June 2018"
[7] "July 2018" "August 2018" "September 2018" "October 2018" "November 2018" "December 2018"
[13] "January 2019" "February 2019" "March 2019" "April 2019"
The other way to do it would be with format applied to seq.Date results:
output <- format( seq( as.Date('2018-01-01'), as.Date('2019-04-01'), by="month") ,
"%B %Y" ) # argument to the format parameter for output
#---------------------
> output
[1] "January 2018" "February 2018" "March 2018" "April 2018" "May 2018" "June 2018"
[7] "July 2018" "August 2018" "September 2018" "October 2018" "November 2018" "December 2018"
[13] "January 2019" "February 2019" "March 2019" "April 2019"
See ?seq.Date and ?format.Date

Answer 3

c(paste(months,"2018"),paste(months,"2019"))[1:17]
## [1] "January 2018" "February 2018" "March 2018" "April 2018" "May 2018" "June 2018"
## [7] "July 2018" "August 2018" "September 2018" "October 2018" "November 2018" "December 2018"
## [13] "January 2019" "February 2019" "March 2019" "April 2019" "May 2019"