Convert week number to date

r as.date
Aaron Soderstrom picture Aaron Soderstrom · Sep 9, 2015 · Viewed 27.4k times · Source

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 2014 and 1. Converting this to a date seems simple: 

as.Date(paste(2014,df$Week,1,sep=""),"%Y%U%u")

But this code only works if week is greater than 9. Week 1 - 9 returns NA. If I change the week to 01,02,03... it still returns NA.

Anyone see what I am missing?

Answer

jeremycg picture jeremycg · Sep 9, 2015

as.Date is calling the 1 to 9 as NA as it is expects two digits for the week number and can't properly parse it.

To fix it, add in some - to split things up:

as.Date(paste(2014, df$Week, 1, sep="-"), "%Y-%U-%u")

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