Convert week number to date

Question

I have a data frame in R with the week of the year that I would like to convert to a date. I know I have to pick a year and a day of the week so I am fixing those values at

Answer 1

An alternative solution is to use date arithmetic from the lubridate package:

lubridate::ymd( "2014-01-01" ) + lubridate::weeks( df$Week - 1 )

The -1 is necessary because 2014-01-01 is already week 1. In other words, we want:

• df$Week == 1 to map to 2014-01-01 (which is ymd("2014-01-01") + weeks(1-1))
• df$Week == 2 to map to 2014-01-08 (which is ymd("2014-01-01") + weeks(2-1))
• and so on.