Converting year and month yyyy-mm format to a date

Question

I have a dataset that looks like this   Month    count 2009-01  12 2009-02  310 2009-03  2379 2009-04  234 2009-05  14 2009-08  1 2009-09  34 2009-10  2386   I want to plot the data  months as x values and counts as y values   Since there are gaps in the data  I want to convert the Information for the Month into a date  I tried   as Date  2009-03     Y- m     But it did not work  Whats wrong  It seems that as Date   requires also a day and is not able to set a standard value for the day  Which function solves my problem

User · Answer

I think  ben-rollert s solution is a good solution    You just have to be careful if you want to use this solution in a function inside a new package    When developping packages  it s recommended to use the syntaxe packagename  function name    see http   kbroman org pkg primer pages depends html     In this case  you have to use the version of as Date   defined by the zoo library    Here is an example      gt  devtools  session info   Session info ----------------------------------------------------------------------------------------------------------------------------------------------------  setting  value                         version  R version 3 3 1  2016-06-21   system   x86 64  linux-gnu             ui       RStudio  1 0 35               language  EN                           collate  C                             tz        lt NA gt                           date     2016-11-09                    Packages --------------------------------------------------------------------------------------------------------------------------------------------------------   package    version date       source          devtools   1 12 0  2016-06-24 CRAN  R 3 3 1   digest     0 6 10  2016-08-02 CRAN  R 3 2 3   memoise    1 0 0   2016-01-29 CRAN  R 3 2 3   withr      1 0 2   2016-06-20 CRAN  R 3 2 3    gt  as Date zoo  as yearmon  1989-10     Y- m     Error in as Date default zoo  as yearmon  1989-10     Y- m         do not know how to convert  zoo  as yearmon  1989-10     Y- m    to class    Date      gt  zoo  as Date zoo  as yearmon  1989-10     Y- m     1   1989-10-01    So if you re developping a package  the good practice is to use     zoo  as Date zoo  as yearmon  1989-10     Y- m

User · Answer

Try this    Here we use text Lines to keep the example self contained but in reality we would replace it with the file name    Lines  lt -  2009-01  12 2009-02  310 2009-03  2379 2009-04  234 2009-05  14 2009-08  1 2009-09  34 2009-10  2386   library zoo  z  lt - read zoo text   Lines  FUN   as yearmon  plot z    The X axis is not so pretty with this data but if you have more data in reality it might be ok or you can use the code for a fancy X axis shown in the examples section of  plot zoo    The zoo series  z  that is created above has a  yearmon  time index and looks like this    gt  z Jan 2009 Feb 2009 Mar 2009 Apr 2009 May 2009 Aug 2009 Sep 2009 Oct 2009        12      310     2379      234       14        1       34     2386     yearmon  can be used alone as well    gt  as yearmon  2000-03    1   Mar 2000    Note     yearmon  class objects sort in calendar order  This will plot the monthly points at equally spaced intervals which is likely what is wanted  however  if it were desired to plot the points at unequally spaced intervals spaced in proportion to the number of days in each month then convert the index of z to  Date  class   time z   lt - as Date time z

User · Answer

Since dates correspond to a numeric value and a starting date  you indeed need the day  If you really need your data to be in Date format  you can just fix the day to the first of each month manually by pasting it to the date   month  lt -  2009-03  as Date paste month  -01  sep

User · Answer

The most concise solution if you need the dates to be in Date format   library zoo  month  lt -  2000-03  as Date as yearmon month    1   2000-03-01    as Date will fix the first day of each month to a yearmon object for you

User · Answer

Using anytime package   library anytime   anydate  2009-01      1   2009-01-01

User · Answer

Indeed  as has been mentioned above  and elsewhere on SO   in order to convert the string to a date  you need a specific date of the month  From the as Date   manual page      If the date string does not specify the date completely  the returned answer may be system-specific  The most common behaviour is to assume that a missing year  month or day is the current one  If it specifies a date incorrectly  reliable implementations will give an error and the date is reported as NA  Unfortunately some common implementations  such as glibc  are unreliable and guess at the intended meaning    A simple solution would be to paste the date  01  to each date and use strptime   to indicate it as the first day of that month     For those seeking a little more background on processing dates and times in R   In R  times use POSIXct and POSIXlt classes and dates use the Date class   Dates are stored as the number of days since January 1st  1970 and times are stored as the number of seconds since January 1st  1970   So  for example   d  lt - as Date  1971-01-01   unclass d     one year after 1970-01-01    1  365  pct  lt - Sys time      in POSIXct unclass pct     number of seconds since 1970-01-01    1  1450276559 plt  lt - as POSIXlt pct  up  lt - unclass plt     up is now a list containing the components of time names up     1   sec      min      hour     mday     mon      year     wday     yday     isdst    zone       11   gmtoff  up hour    1  9   To perform operations on dates and times   plt - as POSIXlt d    Time difference of 16420 61 days   And to process dates  you can use strptime    borrowing these examples from the manual page    strptime  20 2 06 11 16 16 683     d  m  y  H  M  OS      1   2006-02-20 11 16 16 EST     And in vectorized form  dates  lt - c  1jan1960    2jan1960    31mar1960    30jul1960   strptime dates    d b Y      1   1960-01-01 EST   1960-01-02 EST   1960-03-31 EST   1960-07-30 EDT

User · Answer

You could also achieve this with the parse date time or fast strptime functions from the lubridate-package    gt  parse date time dates1   ym    1   2009-01-01 UTC   2009-02-01 UTC   2009-03-01 UTC    gt  fast strptime dates1    Y- m    1   2009-01-01 UTC   2009-02-01 UTC   2009-03-01 UTC    The difference between those two is that parse date time allows for lubridate-style format specification  while fast strptime requires the same format specification as strptime   For specifying the timezone  you can use the tz-parameter    gt  parse date time dates1   ym   tz    CET    1   2009-01-01 CET   2009-02-01 CET   2009-03-01 CET    When you have irregularities in your date-time data  you can use the truncated-parameter to specify how many irregularities are allowed    gt  parse date time dates2   ymdHMS   truncated   3   1   2012-06-01 12 23 00 UTC   2012-06-01 12 00 00 UTC   2012-06-01 00 00 00 UTC      Used data   dates1  lt - c  2009-01   2009-02   2009-03   dates2  lt - c  2012-06-01 12 23   2012-06-01 12   2012-06-01

[r] Converting year and month ("yyyy-mm" format) to a date?

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