R – Convert week number to date

as.dater

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?

Best Answer

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")

Related Solutions

R – Converting year and month (“yyyy-mm” format) to a date

Since dates correspond to a numeric value and a starting date, you indeed need the day. If you really need your data to be in Date format, you can just fix the day to the first of each month manually by pasting it to the date:

month <- "2009-03"
as.Date(paste(month,"-01",sep=""))

R – Convert date to day-of-week in R

You could use lubridate to convert to day of week or day of year.

library(lubridate)

# "02-July-2015" is Thursday
date_string <- "02-July-2015"
dt <- dmy(date_string)
dt
## [1] "2015-07-02 UTC"

### Day of week : (1-7, Sunday is 1)
wday(dt)
## [1] 5

### Day of year (1-366; for 2015, only 365) 
yday(dt)
## [1] 183

### Or a little shorter to do the same thing for Day of year
yday(dmy("02-July-2015"))
## [1] 183

Best Answer

Related Solutions

R – Converting year and month (“yyyy-mm” format) to a date

R – Convert date to day-of-week in R

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