[R] dates() is a great date function in R

Gabor Grothendieck ggrothendieck at gmail.com
Wed Jul 18 21:43:53 CEST 2007

See the Other Applications section of the R News 4/1 help desk
article on dates.

On 7/18/07, Mr Natural <drstrong at ucdavis.edu> wrote:
> Proper calendar dates in R are great for plotting and calculating.
> However for the non-wonks among us, they can be very frustrating.
> I have recently discussed the pains that people in my lab have had
> with dates in R. Especially the frustration of bringing date data into R
> from Excel, which we have to do a lot.
> Please find below a simple analgesic for R date importation that I
> discovered
> over the last 1.5 days (Learning new stuff in R is calculated in 1/2 days).
> The function    dates()    gives the simplest way to get calendar dates into
> R from Excel that I can find.
> But straight importation of Excel dates, via a csv or txt file, can be a a
> huge pain (I'll give details for anyone who cares to know).
> My pain killer is:
> Consider that you have Excel columns in month, day, year format. Note that R
> hates date data that does not lead with the year.
> a. Load the chron library by typing   library(chron)   in the console.
> You know that you need this library from information revealed by
> performing the query,
> ?dates()"    in the Console window. This gives the R documentation
> help file for this and related time, date functions.  In the upper left
> of the documentation, one sees "dates(chron)". This tells you that you
> need the library chron.
> b. Change the format "dates" in Excel to format "general", which gives
> 5 digit Julian dates. Import the csv file (I use    read.csv()  with the
> Julian dates and other data of interest.
> c.  Now, change the Julian dates that came in with the csv file into
> calendar dates with the    dates() function. Below is my code for performing
> this activity, concerning an R data file called ss,
> ss holds the Julian dates, illustrated below from the column MPdate,
> >ss$MPdate[1:5]
> [1] 34252 34425 34547 34759 34773
> The dates() function makes calendar dates from Julian dates,
> >dmp<-dates(ss$MPdate,origin=c(month = 1, day = 1, year = 1900))
> > dmp[1:5]
> [1] 10/12/93 04/03/94 08/03/94 03/03/95 03/17/95
> I would appreciate the comments of more sophisticated programmers who
> can suggest streamlining or shortcutting this operation.
> regards, Don
> --
> View this message in context: http://www.nabble.com/dates%28%29-is-a-great-date-function-in-R-tf4105322.html#a11675205
> Sent from the R help mailing list archive at Nabble.com.
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