Find the day of a week

Question

Let's say that I have a date in R and it's formatted as follows.

   date      

2012-02-01 

2012-02-01

2012-02-02

Is there any way in R to add another column with the day of the week associated with the date? The dataset is really large, so it would not make sense to go through manually and make the changes.

df = data.frame(date=c("2012-02-01", "2012-02-01", "2012-02-02")) 

So after adding the days, it would end up looking like:

   date       day

2012-02-01   Wednesday

2012-02-01   Wednesday

2012-02-02   Thursday

Is this possible? Can anyone point me to a package that will allow me to do this? Just trying to automatically generate the day by the date.

Answer 1

To extract the weekday, month or quarter, or the Julian time (days since some origin), use the weekdays function that extracts parts of a POSIXt or Date Object.

In your case:

dt = data.frame(date=c("2012-02-01", "2012-02-01", "2012-02-02")) 

dt$day <- weekdays(as.Date(dt$date))

dt

Output:

        date       day

1 2012-02-01 Wednesday

2 2012-02-01 Wednesday

3 2012-02-02  Thursday