On 04/07/2013 11:36, Dante.py wrote: > They are really good methods. Thank you very much. > Could I ask one more question. Is there obvious difference between these > two methods?
Yes. It is obvious that the type of x differs. > > > 2013/7/4 Prof Brian Ripley <rip...@stats.ox.ac.uk > <mailto:rip...@stats.ox.ac.uk>> > > On 04/07/2013 08:04, Dante.py wrote: > > I have a method which is not so smart --use grep to match the > pattern. > for example: > dates <- c("02/27/92", "02/27/92", "01/14/92", "02/28/92", > "02/01/91") > day <- as.Date(dates, "%m/%d/%y") > day: > [1] "1992-02-27" "1992-02-27" "1992-01-14" "1992-02-28" "1991-02-01" > If I want to search for 1991, I can use: > grep("1991-*", day) > > > Hope for a better solution. > > > Here are 2. The first is quite obvious, the second is faster but > needs more knowledge. > > x <- format(day, "%Y") > day[x >= "2007" & x <= "2009"] > > x <- as.POSIXlt(day)$year + 1900 > day[x >= 2007 & x <= 2009] > > > > > 2013/7/4 Gallon Li <gallon...@gmail.com > <mailto:gallon...@gmail.com>> > > i have converted my data into date format like below: > > day=as.Date(originaldate,"%m/%__d/%Y") > day[1:5] > > [1] "2008-04-12" "2011-07-02" "2011-09-02" "2008-04-12" > "2008-04-12" > > I wish to select only those observations from 2007 to 2009, > how can I > select from this list? > > [[alternative HTML version deleted]] > > ________________________________________________ > R-help@r-project.org <mailto:R-help@r-project.org> mailing list > https://stat.ethz.ch/mailman/__listinfo/r-help > <https://stat.ethz.ch/mailman/listinfo/r-help> > PLEASE do read the posting guide > http://www.R-project.org/__posting-guide.html > <http://www.R-project.org/posting-guide.html> > and provide commented, minimal, self-contained, reproducible > code. > > > > > > > ________________________________________________ > R-help@r-project.org <mailto:R-help@r-project.org> mailing list > https://stat.ethz.ch/mailman/__listinfo/r-help > <https://stat.ethz.ch/mailman/listinfo/r-help> > PLEASE do read the posting guide > http://www.R-project.org/__posting-guide.html > <http://www.R-project.org/posting-guide.html> > and provide commented, minimal, self-contained, reproducible code. > > > > -- > Brian D. Ripley, rip...@stats.ox.ac.uk <mailto:rip...@stats.ox.ac.uk> > Professor of Applied Statistics, > http://www.stats.ox.ac.uk/~__ripley/ > <http://www.stats.ox.ac.uk/~ripley/> > University of Oxford, Tel: +44 1865 272861 > <tel:%2B44%201865%20272861> (self) > 1 South Parks Road, +44 1865 272866 <tel:%2B44%201865%20272866> (PA) > Oxford OX1 3TG, UK Fax: +44 1865 272595 > <tel:%2B44%201865%20272595> > > > > > -- > 张晔 Dante.py > 中山大学09级数学与应用数学专业 > 个人主页:http://dantepy.yslsg.org/ -- Brian D. Ripley, rip...@stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-help@r-project.org mailing list 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.