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

User · Answer

Look up  strftime       A Full weekday name in the current locale   df day   strftime df date   A

User · Answer

This should do the trick  df   data frame date c  2012-02-01    2012-02-01    2012-02-02     dow  lt - function x  format as Date x     A   df day  lt - dow df date  df   Returns          date       day 1 2012-02-01 Wednesday 2 2012-02-01 Wednesday 3 2012-02-02  Thursday

User · Answer

df   data frame date c  2012-02-01    2012-02-01    2012-02-02     df day  lt - 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

User · Answer

Use the lubridate package and function wday   library lubridate  df date  lt - as Date df date  wday df date  label TRUE   1  Wed   Wed   Thurs Levels  Sun  lt  Mon  lt  Tues  lt  Wed  lt  Thurs  lt  Fri  lt  Sat

User · Answer

start   as POSIXct  2017-09-01   end   as POSIXct  2017-09-06    dat   data frame Date   seq POSIXt from   start                                     to   end                                     by    DSTday       see  strptime for details of formats you can extract    day of the week as numeric  Monday is 1  dat weekday1   as numeric format dat Date  format     u       abbreviated weekday name dat weekday2   format dat Date  format     a      full weekday name dat weekday3   format dat Date  format     A    dat   returns     Date       weekday1 weekday2  weekday3 1 2017-09-01        5      Fri    Friday 2 2017-09-02        6      Sat    Saturday 3 2017-09-03        7      Sun    Sunday 4 2017-09-04        1      Mon    Monday 5 2017-09-05        2      Tue    Tuesday 6 2017-09-06        3      Wed    Wednesday

User · Answer

form comment of JStrahl format as Date df date    w    we get number of current day   as numeric format as Date  2016-05-09     w

User · Answer

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

[r] Find the day of a week

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