[R] extracting months from a data

[Dalthorp, Daniel]

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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