How to extract Month from date in R

Question

I am using the lubridate package and applying the month function to extract month from date  I ran the str command on date field and I got   Factor w  9498 levels  01 01 1979   01 01 1980      5305 1 1 1 1 1 1 1 1 1       gt  v1 Date lt -month v1 Date  Error in as POSIXlt character as character x           character string is not in a standard unambiguous format   Here is an example of my data frame  https   drive google com file d 0B6cqWmwsEk20Q2dHblhXZi14Wk0 edit usp sharing  I don t know what I am doing wrong

User · Answer

Without the need of an external package   if your date is in the following format   myDate   as POSIXct  2013-01-01     Then to get the month number    format myDate   m     And to get the month string   format myDate   B

User · Answer

Her is another R base approach   From your example  Some date   Some date lt - 01 01 1979    We tell R   That is a Date   Some date lt -as Date Some date    We extract the month   months Some date   output   1   January    Finally  we can convert it to a numerical variable   as numeric as factor months Some date     outpt   1  1

User · Answer

month states      Date-time must be a POSIXct  POSIXlt  Date  Period  chron  yearmon    yearqtr  zoo  zooreg  timeDate  xts  its  ti  jul  timeSeries  and fts   objects    Your object is a factor  not even a character vector  presumably because of stringsAsFactors   TRUE   You have to convert your vector to some datetime class  for instance to POSIXlt   library lubridate  some date  lt - c  01 02 1979    03 04 1980   month as POSIXlt some date  format   d  m  Y     1  2 4   There s also a convenience function dmy  that can do the same  tip proposed by  Henrik     month dmy some date    1  2 4   Going even further   IShouldBuyABoat gives another hint that dd mm yyyy character formats are accepted without any explicit casting   month some date   1  2 4   For a list of formats  see  strptime  You ll find that  standard unambiguous format  stands for     The default formats follow the rules of the ISO 8601 international   standard which expresses a day as  2001-02-28  and a time as    14 01 02  using leading zeroes as here

User · Answer

you can convert it into date format by-  new date lt - as Date old date    m  d  Y       from new date  you can get the month by strftime    month lt - strftime new date    m    old date lt -  01 01 1979  new date lt - as Date old date    m  d  Y   new date   1   1979-01-01  month lt - strftime new date   m   month   1   01  year lt - strftime new date    Y   year   1   1979

User · Answer

For some time now  you can also only rely on the data table package and its IDate class plus associated functions   Check  as IDate     So  no need to additionally install lubridate  require data table   some date  lt - c  quot 01 02 1979 quot    quot 03 04 1980 quot   month as IDate some date    d  m  Y      all data table functions

[r] How to extract Month from date in R

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