Find the day of a week
date, r, r-faq
Solution
df = data.frame(date=c("2012-02-01", "2012-02-01", "2012-02-02"))
df$day <- weekdays(as.Date(df$date))
df
## date day
## 1 2012-02-01 Wednesday
## 2 2012-02-01 Wednesday
## 3 2012-02-02 Thursday
Edit: Just to show another way...
The `wday` component of a `POSIXlt` object is the numeric weekday (0-6 starting on Sunday).
as.POSIXlt(df$date)$wday
## [1] 3 3 4
which you could use to subset a character vector of weekday names
c("Sunday", "Monday", "Tuesday", "Wednesday", "Thursday",
"Friday", "Saturday")[as.POSIXlt(df$date)$wday + 1]
## [1] "Wednesday" "Wednesday" "Thursday"
Problem
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.