Try this: > e <- expression(Sepal.Width > 4) > subset(iris, eval(e), select = "Sepal.Length") Sepal.Length 16 5.7 33 5.2 34 5.5 > subset(iris, eval(e)) Sepal.Length Sepal.Width Petal.Length Petal.Width Species 16 5.7 4.4 1.5 0.4 setosa 33 5.2 4.1 1.5 0.1 setosa 34 5.5 4.2 1.4 0.2 setosa
On Mon, Aug 11, 2008 at 9:36 PM, Dries Knapen <[EMAIL PROTECTED]> wrote: > Hi, > > Based on user input, I wrote a function that creates a list which looks > like: > >> str(list) > List of 4 > $ varieties: chr [1:12] "temp.26_time.5dagen_biorep.1" > "time.5dagen_temp.26_biorep.2" "temp.18_time.5dagen_biorep.1" > "temp.18_time.5dagen_biorep.2" ... > $ temp : Factor w/ 2 levels "18","26": 2 2 1 1 2 2 1 1 1 1 ... > $ time : Factor w/ 3 levels "14dagen","28dagen",..: 3 3 3 3 1 1 1 1 2 2 > ... > $ biorep : Factor w/ 2 levels "1","2": 1 2 1 2 1 2 1 2 1 2 ... > > Now, based on user input as well, I want to dynamically extract data from > list$varieties. Therefore, I wrote a function which generates a string > containing the data extraction conditions which looks like this: > >> query <- make.contrast.substring(negative.contrast, list) > Read 1 item > [1] > "(list$temp=='18')&(list$time=='14dagen'|list$time=='28dagen'|list$time=='5dagen')&(list$biorep=='1'|list$biorep=='2')" > > Now what I want to achieve is to extract data by doing: > > list$varieties[query] > > which doesn't work since "query" is a string and object names are not > expanded... > > Obviously, manually copying the string like so > > list$varieties[(list$temp=='18')&(list$time=='14dagen'|list$time=='28dagen'|list$time=='5dagen')&(list$biorep=='1'|list$biorep=='2')] > > works perfectly - but I need it to be automated. > > I'm quite new to R and used to programming in PHP, so I may just be > "conceptually" confused about how to do this. Any help would be greatly > appreciated. > > thanks in advance, > Dries Knapen > > > > ******************************************** > Dr. Dries Knapen > > University of Antwerp > Department of Biology > Ecophysiology, Biochemistry and Toxicology > Groenenborgerlaan 171 - U711, B-2020 Antwerp > Belgium > > tel ++32 3 265 33 49 > fax ++32 3 265 34 97 > > ______________________________________________ > 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.
