Jeffrey Robert Spies <[EMAIL PROTECTED]> writes: > I would personally use the following method (example using the iris > data included with R): > > data(iris) > tSelect <- (iris$Sepal.Length > 6.0 & iris$Sepal.Length < 6.2 & iris > $Sepal.Width == 3.0) > tSelectedData <- iris[tSelect,] > > Then you can simply work with tSelectedData for whatever equation > you use, i.e.: > > tSelectedData$Sepal.Length - tSelectedData$Sepal.Width > > Of course you could write all of this on one line, but that doesn't > read well. > > Hope that helps,
But why not use subset()? For a neat way around the as.Date business, consider between <- function(x,x1,x2) x >= x1 & x < x2 begin <- as.Date("2004-04-22") end <- as.Date("2004-09-01") before2sw <- subset(energy.data, between(as.Date(start, format="%d-%b-%y"), begin, end) & temp < 65) > Jeff. > > On Oct 26, 2006, at 3:55 PM, Zembower, Kevin wrote: > > > There must be a better way to select the rows after 22-Apr-2004 and > > before 01-Sep-2004 with a temperature below 65 than this: > > > >> before2sw1 <- subset(energy.data, as.Date(start, format="%d-%b-%y") < > > as.Date("01-Sep-04", format = "%d-%b-%y")) > >> before2sw2 <- subset(before2sw1, as.Date(start, format="%d-%b-%y") >= > > as.Date("22-Apr-04", format = "%d-%b-%y"), select=c(therms,temp,days)) > >> before2sw <- subset(before2sw2, temp < 65) > > > > Is it also possible to combine in this step: > > > > attach(before2sw) > > before2sw.HDD <- therms / (65 - temp) * days > > > > My data looks like this: > >> head(energy.data) > > start therms gas KWHs elect temp days > > 1 10-Jun-98 9 16.84 613 63.80 75 40 > > 2 20-Jul-98 6 15.29 721 74.21 76 29 > > 3 18-Aug-98 7 15.73 597 62.22 76 29 > > 4 16-Sep-98 42 35.81 460 43.98 70 33 > > 5 19-Oct-98 105 77.28 314 31.45 57 29 > > 6 17-Nov-98 106 77.01 342 33.86 48 30 > >> > > > > Thanks for your suggestions and advice. I'm continuing to enjoy > > learning > > R. > > > > -Kevin > > > > Kevin Zembower > > Internet Services Group manager > > Center for Communication Programs > > Bloomberg School of Public Health > > Johns Hopkins University > > 111 Market Place, Suite 310 > > Baltimore, Maryland 21202 > > 410-659-6139 > > > > ______________________________________________ > > R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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. > -- O__ ---- Peter Dalgaard Ă˜ster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ R-help@stat.math.ethz.ch 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.