Hello,
Your "eval(tests$rule[1])" needs a slight modification to get the results. Try this: tests<-read.table(text=" rule info$country=='Greenland' info$age>50 ",sep="",header=TRUE,stringsAsFactors=FALSE) info<-data.frame(first=rep(NA,5),country=c("GReenland","Iceland","Ireland","Greenland","Greenland") ,age=c(30,55,66,79,80),name=c("Mary","Paul","Robert","John","Ivan")) #1st condition eval(parse(text=tests$rule[1])) [1] FALSE FALSE FALSE TRUE TRUE #2nd condition eval(parse(text=tests$rule[2])) [1] FALSE TRUE TRUE TRUE TRUE # tests[1,1] condition: subset info info[eval(parse(text=tests$rule[1])),] first country age name 4 NA Greenland 79 John 5 NA Greenland 80 Ivan #tests[2,1] condition: subset info info[eval(parse(text=tests$rule[2])),] first country age name 2 NA Iceland 55 Paul 3 NA Ireland 66 Robert 4 NA Greenland 79 John 5 NA Greenland 80 Ivan A.K. ----- Original Message ----- From: New RUser <newruser2...@gmail.com> To: r-help@r-project.org Cc: Sent: Tuesday, July 3, 2012 12:24 PM Subject: [R] "evaluating expressions" contained in a dataframe #I have a dataframe called "tests" that contain "character expressions". These characters are rules that use data from within another dataframe. Is there any way within R I can access the rules in the dataframe called tests, and then "evaluate" these "rules"? #An example may better explain what I am trying to accomplish: tests <- data.frame(matrix(data=c("info$country == 'Greenland'", "info$age > 50"), nrow=2, ncol=1)) names(tests) <- "rule" info <- data.frame(matrix(data=NA, nrow=5, ncol=3)) names(info) <- c("first", "country", "age") info$name <- c("Mary", "Paul", "Robert", "John", "Ivan") info$country <- c("GReenland", "Iceland", "Ireland", "Greenland", "Greenland") info$age <- c(30, 55, 66, 79, 80) #e.g. for "info$country == 'Greenland'" #I want: info$country == 'Greenland' [1] FALSE FALSE FALSE TRUE TRUE #e.g. info$country == 'Greenland' info$age > 50 #I tried this, but it does not "work": eval(tests$rule[1]) [[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.