On Tue, 2007-09-11 at 19:56 +0300, Tolga Uzuner wrote: > Dear R-Users, > > Have a question about reading in some data and manipulating dates. I > have a data set in excel which looks like this: > > Date PEG ETN HSP PTC > 13/10/2004 41.92 64.75 29.86 9.27 > 14/10/2004 41.93 61.79 29.98 9.14 > 15/10/2004 41.69 62.7 30.09 9.04 > 18/10/2004 41.37 62.14 30.39 8.96 > 19/10/2004 41.01 61.98 29.61 9.02 > 20/10/2004 41.01 61.98 30.25 9 > > I have used read.table by saving the sheety above in tab format to > read this in but am > having some difficulties: > - the dates above do not seem to be getting read in in date format: > how can I force this ?
For the first question (I'm not sure how to do the second): We use read.table() to read in the data from file (here I saved your data as tab delimited file 'temp.csv'. Argument as.is = TRUE is used to stop R converting character strings (i.e. the Date column here) to factors; this saves us a step later converting them back. > dat <- read.table("temp.csv", sep = "\t", as.is = TRUE, header = TRUE) Data read in OK: > dat Date PEG ETN HSP PTC 1 13/10/2004 41.92 64.75 29.86 9.27 2 14/10/2004 41.93 61.79 29.98 9.14 3 15/10/2004 41.69 62.70 30.09 9.04 4 18/10/2004 41.37 62.14 30.39 8.96 5 19/10/2004 41.01 61.98 29.61 9.02 6 20/10/2004 41.01 61.98 30.25 9.00 Use as.Date() to convert the character strings to a vector of class 'Date'. The format argument tells R how the dates are formatted in the character strings you just read in. The %d, %m bits etc are place holders describing the date parts, but the "/" characters are literal - if your dates were formatted "20-10-2004", you would use format = "%d-% m-%Y". See ?strftime for how to specify 'format' if you have dates formatted in other ways (say with month name instead of number). > dat$Date <- as.Date(dat$Date, format = "%d/%m/%Y") Note that now dat$Date is now an object of class 'Date': > str(dat) 'data.frame': 6 obs. of 5 variables: $ Date:Class 'Date' num [1:6] 12704 12705 12706 12709 12710 ... $ PEG : num 41.9 41.9 41.7 41.4 41.0 ... $ ETN : num 64.8 61.8 62.7 62.1 62.0 ... $ HSP : num 29.9 30.0 30.1 30.4 29.6 ... $ PTC : num 9.27 9.14 9.04 8.96 9.02 9 Which R will treat appropriately in plots for example: > plot(PEG ~ Date, data = dat, type = "l") HTH G -- %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% Gavin Simpson [t] +44 (0)20 7679 0522 ECRC, UCL Geography, [f] +44 (0)20 7679 0565 Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/ UK. WC1E 6BT. [w] http://www.freshwaters.org.uk %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% ______________________________________________ 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.