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

Answer 1

Let's say you additionally want the week to begin on Monday (instead of default on Sunday), then the following is helpful:

require(lubridate)
df$day = ifelse(wday(df$time)==1,6,wday(df$time)-2)

The result is the days in the interval [0,..,6].

If you want the interval to be [1,..7], use the following:

df$day = ifelse(wday(df$time)==1,7,wday(df$time)-1)

... or, alternatively:

df$day = df$day + 1