Noone has yet mentioned tjhe 'standard' way to reference a data frame item, which uses $
boxplot(CB_un[["Value]]~CB_un[["State.Fips"]]) #Note the double [[ ]] # is equivalent to boxplot(CB_un$Value~CB_un$State.Fips) # and can be achieved by boxplot(Value~State.Fips, data=CB_un) The rather awkward [["name"]] notation is usually only needed if the name does not comply with variable naming requirements (including list and data frame names); for example, names containing spaces or operator symbols (like "+") are not allowed for ordinary variables. It is possible and sometimes useful to create non-standard data frame names for display; for example, anova.lm actually returns a data frame with names "Df", "Sum Sq", "Mean Sq", F value" and "Pr(>F)". But it makes manipulation a tad trickier and you'd be unable to use them in the context of a formula with a data argument. S Ellison > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Samantha Sifleet > Sent: 11 June 2012 17:29 > To: [email protected] > Subject: [R] Why is my data always imported as a list? > > Hi, > > I am a relatively new to R. So, this is probably a really > basic issue that I keep hitting. > > I read my data into R using the read.csv command: > > x = rep("numeric", 3) > CB_un=read.csv("Corn_Belt_unirr.csv", header=TRUE, > colClasses=c("factor", > x)) > > # I have clearly told R that I have one factor variable and 3 > numeric variables in this table. > #but if I try to do anything with them, I get an error > > boxplot(CB_un["Value"]~CB_un["State.Fips"]) > > Error in model.frame.default(formula = CB_un["Value"] ~ > CB_un["State.Fips"]) : > invalid type (list) for variable 'CB_un["Value"]' > > # Because these variables are all stored as lists. > #So, I have to unpack them. > > CB_unirr_rent<-as.numeric(unlist(CB_un["Value"])) > CB_unirr_State<-as.factor(unlist(CB_un["State.Fips"])) > > #before I can do anything with them > > boxplot(CB_unirr_rent~CB_unirr_State) > > Is there a reason my data is always imported as lists? Is > there a way to skip this upacking step? > > Thanks, > > Sam > [[alternative HTML version deleted]] > > ______________________________________________ > [email protected] 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. > ******************************************************************* This email and any attachments are confidential. Any use...{{dropped:8}} ______________________________________________ [email protected] 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.
