raw <- read.csv(file=filename, head=TRUE,sep=",") I've read in a csv file, and I'm looking to access a column whose name is held in a string. For example, I want to access raw$one or raw$two, but this will depending on the string. Let's say that the string is decision<-"one". How would I access raw$one? The following doesn't work: numbers<-raw$decision Please help me! Thanks! -- View this message in context: http://www.nabble.com/Accessing-a-field-in-a-data-fram-tp18244661p18244661.html Sent from the R help mailing list archive at Nabble.com.
?"[[" decision <- "one" raw[[decision]] On Wed, Jul 2, 2008 at 3:10 PM, R_Learner <sschiang8 at gmail.com> wrote:> > raw <- read.csv(file=filename, head=TRUE,sep=",") > > I've read in a csv file, and I'm looking to access a column whose name is > held in a string. > > For example, I want to access raw$one or raw$two, but this will depending on > the string. Let's say that the string is decision<-"one". How would I access > raw$one? > > The following doesn't work: > numbers<-raw$decision > > Please help me! > Thanks! > -- > View this message in context: http://www.nabble.com/Accessing-a-field-in-a-data-fram-tp18244661p18244661.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help at 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. >-- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve?
on 07/02/2008 02:10 PM R_Learner wrote:> raw <- read.csv(file=filename, head=TRUE,sep=",") > > I've read in a csv file, and I'm looking to access a column whose name is > held in a string. > > For example, I want to access raw$one or raw$two, but this will depending on > the string. Let's say that the string is decision<-"one". How would I access > raw$one? > > The following doesn't work: > numbers<-raw$decision > > Please help me! > Thanks!> str(iris) 'data.frame': 150 obs. of 5 variables: $ Sepal.Length: num 5.1 4.9 4.7 4.6 5 5.4 4.6 5 4.4 4.9 ... $ Sepal.Width : num 3.5 3 3.2 3.1 3.6 3.9 3.4 3.4 2.9 3.1 ... $ Petal.Length: num 1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 ... $ Petal.Width : num 0.2 0.2 0.2 0.2 0.2 0.4 0.3 0.2 0.2 0.1 ... $ Species : Factor w/ 3 levels "setosa","versicolor",..: 1 1 1 1 1 1 1 1 1 1 ... MyCol <- "Petal.Length" # Use column indexing > iris[, MyCol] [1] 1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 1.5 1.6 1.4 1.1 1.2 1.5 [17] 1.3 1.4 1.7 1.5 1.7 1.5 1.0 1.7 1.9 1.6 1.6 1.5 1.4 1.6 1.6 1.5 ... # Use list indexing. A data frame is a list... > iris[[MyCol]] [1] 1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 1.5 1.6 1.4 1.1 1.2 1.5 [17] 1.3 1.4 1.7 1.5 1.7 1.5 1.0 1.7 1.9 1.6 1.6 1.5 1.4 1.6 1.6 1.5 # Use subset() > subset(iris, select = MyCol) Petal.Length 1 1.4 2 1.4 3 1.3 4 1.5 5 1.4 ... See ?"[.data.frame" and ?subset HTH, Marc Schwartz