You need to review all the items I already mentioned. The % codes are in ?strptime so just use those appropraite to your format.
The R manuals, the books listed here: http://www.r-project.org/doc/bib/R-publications.html and the Contributed Documentation: http://cran.r-project.org/other-docs.html are among the items you can use to learn R. On Mon, Jul 21, 2008 at 10:41 AM, Williams, Robin <[EMAIL PROTECTED]> wrote: > And following on from my original question: > In another file I have the dates in numeric format, (ddmmyy). How could > I extract the data between 01/05/97 and 30/09/97, etc? Do I need to > implement some sort of loop? > > > Robin Williams > Met Office summer intern - Health Forecasting > [EMAIL PROTECTED] > -----Original Message----- > From: Gabor Grothendieck [mailto:[EMAIL PROTECTED] > Sent: Monday, July 21, 2008 3:26 PM > To: Williams, Robin > Cc: R-help@r-project.org > Subject: Re: [R] Subsetting data by date > > Continuing on, to just get points from May to Sep > > mo <- as.numeric(format(time(z), "%m")) > z.summer <- z[mo >= 5 & mo <= 9] > > If in your case z is multivariate rather than univariate (as it is in > our example) then it would be: > z.summer <- z[mo >= 5 & mo <= 9, ] > > On Mon, Jul 21, 2008 at 9:55 AM, Gabor Grothendieck > <[EMAIL PROTECTED]> wrote: >> Try this: >> >> Lines <- "Date,Temp >> 1-Apr-1997,50 >> 3-Sept-2001,60" >> >> library(zoo) >> >> # function to reduce 4 char mos to 3 char convert.date <- function(x, >> format) as.Date(sub("(-...).-", "\\1-", x), format) >> >> # z <- read.zoo("myfile.csv", header = TRUE, sep = ",", FUN = >> convert.date, format = "%d-%b-%Y") z <- >> read.zoo(textConnection(Lines), header = TRUE, sep = ",", FUN = >> convert.date, format = "%d-%b-%Y") >> >> plot(z) >> >> If the dates are actually three letters, i.e. Sep and not Sept, then >> you could eliminate convert.date and simplify the read.zoo line to: >> >> z <- read.zoo(textConnection(Lines), header = TRUE, sep = ",", format >> = "%d-%b-%Y") >> >> See the zoo package documentation and its three vignettes as well as >> ?read.zoo ?strptime and ?plot.zoo and also look at the dates article > in R News 4/1. >> >> >> On Mon, Jul 21, 2008 at 9:31 AM, Williams, Robin >> <[EMAIL PROTECTED]> wrote: >>> Hi all, >>> Firstly I appologise if this question has been answered previously, >>> however searching of the archives and the internet generally has not >>> yielded any results. >>> >>> I am looking in to the effects of summer weather conditions >>> (temperature, humidity etc), on the incidences of a breathing >>> disorder brought on through smoking (COPD). I am fairly new to R and >>> completely new to the idea of writing R scripts, subsetting >>> dataframes etc. I am working on a 12 week summer placement at the Met > >>> Office, UK, having just finished my second year of a mathematics > course at university. >>> >>> Basically I have data between January 1 1997 and December 31 2007. >>> However as I am only interest in the summer months (which I have >>> defined to be between May 1 and September 30), I would like to >>> extract the relevant data in R in a timely manner. Obviously I could >>> go and open my csv files in excel, cut and paste the relevant data, >>> etc, however I would like to maximise R's potential as I feel it will > >>> stand me in better stead in the long run. >>> Currently the dates are in the form >>> 1-Apr-1997, >>> 3-Sept-2001, >>> etc. >>> I will create a data.frame with date as one of the variables, the >>> others being (initially) temperature, humidity, and Admissions (the >>> number of hospital admissions for COPD exaserbations). >>> Please could somebody tell me if there is a simple way to extract >>> the data I want, and if so perhaps a sample command to get me going? >>> Do I first need to format the dates to some numeric-only format? As I > >>> say, I could use Excel to create the files in the right format, but I > >>> will be dealing with a lot more variables in the future (perhaps up >>> to 8) and so this will become a pain-staking process. >>> >>> Please reply either on or off list. >>> >>> Many thanks for any help. >>> Robin Williams >>> Met Office summer intern - Health Forecasting >>> [EMAIL PROTECTED] >>> >>> >>> [[alternative HTML version deleted]] >>> >>> ______________________________________________ >>> 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. >>> >> > ______________________________________________ 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.
