[R] extracting months from a data

[Jeff Newmiller]

How about slower? That is objective.

I use dates all the time so I am quite familiar with what they are good for. However,  I prefer to avoid inventing information such as which year the date should have included unless I have to based on knowledge of the data source. It is not good to mislead the consumer of output about the existence of year information if it wasn't there to begin with. 
-- 
Sent from my phone. Please excuse my brevity.

On March 9, 2016 4:49:18 PM PST, "Dalthorp, Daniel" <ddalthorp at usgs.gov> wrote:
>Good point about 29-Feb...fixed in the following:
>
>format(as.Date(paste0(x,"-2016"),format='%d-%b-%Y'),'%b')
>
># Also: The date functions can be used to easily calculate passage of
>time
>and offer good flexibility for formatting output.
>
>-Dan
>
>P.S. "harder to understand" is in the eye of the beholder (as is
>"recommended").
>
>
>
>On Wed, Mar 9, 2016 at 4:39 PM, Jeff Newmiller
><jdnewmil at dcn.davis.ca.us>
>wrote:
>
>> Still not recommended. That takes more steps, is harder to
>understand, and
>> will break when given "29-Feb" as input.
>> --
>> Sent from my phone. Please excuse my brevity.
>>
>> On March 9, 2016 4:15:31 PM PST, "Dalthorp, Daniel"
><ddalthorp at usgs.gov>
>> wrote:
>>>
>>> Or:
>>>
>>> x <- c( "3-Oct", "10-Nov" )
>>>
>format(as.Date(paste0(x,rep("-1970",length(x))),format='%d-%b-%Y'),'%b')
>>>
>>> # the 'paste0' appends a year to the text vector
>>> # the 'as.Date' interprets the strings as dates with format 
>10-Jun-2016
>>> (e.g.)
>>> # the 'format' returns a string with date in format '%b' (which is
>just
>>> the name of the month)
>>>
>>> On Wed, Mar 9, 2016 at 3:52 PM, Jeff Newmiller
><jdnewmil at dcn.davis.ca.us>
>>> wrote:
>>>
>>>> Your dates are incomplete (no year) so I suggest staying away from
>the
>>>> date functions for this. Read ?regex and ?sub.
>>>>
>>>> x <- c( "3-Oct", "10-Nov" )
>>>> m <- sub( "^\\d+-([A-Za-z]{3})$", "\\1", x )
>>>>
>>>> --
>>>> Sent from my phone. Please excuse my brevity.
>>>>
>>>> On March 9, 2016 10:14:25 AM PST, KMNanus <kmnanus at gmail.com>
>wrote:
>>>> >I have a series of dates in  format 3-Oct, 10-Oct, 20-Oct, etc.
>>>> >
>>>> >I want to create a variable of just the month.  If I convert the
>date
>>>> >to a character string, substr is ineffective because some of the
>dates
>>>> >have 5 characters (3-Oct) and some have 6 (10-Oct).
>>>> >
>>>> >Is there a date function that accomplishes this easily?
>>>> >
>>>> >Ken
>>>> >kmnanus at gmail.com
>>>> >914-450-0816 (tel)
>>>> >347-730-4813 (fax)
>>>> >
>>>> >
>>>> >
>>>> >______________________________________________
>>>> >R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>>> >https://stat.ethz.ch/mailman/listinfo/r-help
>>>> >PLEASE do read the posting guide
>>>> >http://www.R-project.org/posting-guide.html
>>>> >and provide commented, minimal, self-contained, reproducible code.
>>>>
>>>>         [[alternative HTML version deleted]]
>>>>
>>>> ______________________________________________
>>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>> PLEASE do read the posting guide
>>>> http://www.R-project.org/posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>
>>>
>>>
>>>
>>> --
>>> Dan Dalthorp, PhD
>>> USGS Forest and Rangeland Ecosystem Science Center
>>> Forest Sciences Lab, Rm 189
>>> 3200 SW Jefferson Way
>>> Corvallis, OR 97331
>>> ph: 541-750-0953
>>> ddalthorp at usgs.gov
>>>
>>>
>
>
>-- 
>Dan Dalthorp, PhD
>USGS Forest and Rangeland Ecosystem Science Center
>Forest Sciences Lab, Rm 189
>3200 SW Jefferson Way
>Corvallis, OR 97331
>ph: 541-750-0953
>ddalthorp at usgs.gov

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