Subset data frame by date

Question

I have a dataset called EPL2011 12  I would like to make new a dataset by subsetting the original  by date   The dates are in the column named Date  The dates are in DD-MM-YY format    I have tried   EPL2011 12FirstHalf  lt - subset EPL2011 12  Date  gt  13-01-12    and  EPL2011 12FirstHalf  lt - subset EPL2011 12  Date  gt   13-01-12     but get this error message each time      Warning message  In Ops factor Date  13- 1 - 12     gt  not meaningful for factors    I guess that means R is treating like text instead of a number and that why it won t work

User · Accepted Answer

Well  it s clearly not a number since it has dashes in it  The error message and the two comments tell you that it is a factor but the commentators are apparently waiting and letting the message sink in  Dirk is suggesting that you do this    EPL2011 12 Date2  lt - as Date  as character EPL2011 12 Date     d- m- y     After that you can do this    EPL2011 12FirstHalf  lt - subset EPL2011 12  Date2  gt  as Date  2012-01-13       R date functions assume the format is either  YYYY-MM-DD  or  YYYY MM DD   You do need to compare like classes  date to date   or character to character

User · Answer

The first thing you should do with date variables is confirm that R reads it as a Date  To do this  for the variable  i e  vector column  called Date  in the data frame called EPL2011 12  input  class EPL2011 12 Date   The output should read  1   Date   If it doesn t  you should format it as a date by inputting   EPL2011 12 Date  lt - as Date EPL2011 12 Date    d- m- y    Note that the hyphens in the date format    d- m- y   above can also be slashes    d  m  y    Confirm that R sees it as a Date  If it doesn t  try a different formatting command  EPL2011 12 Date  lt - format EPL2011 12 Date  format   d  m  y    Once you have it in Date format  you can use the subset command  or you can use brackets  WhateverYouWant  lt - EPL2011 12 EPL2011 12 Date  gt  as Date  2014-12-15

[r] Subset data.frame by date

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