Yes, I think you are overcomplicating: it's perfectly valid to subscript by names. (In fact, it's generally preferred to trying to use the $ for programming because it's so much more flexible) I.e.,
lapply( phList, function(df) get(df)[, c("ID", "DATE_DISPENSED", "TG_NAME1", "TG_NAME2", "TG_NAME3")] ) This will go through each element of phList, get the object by that name, and pull out the columns with the given names. Then it will return to you a list with the results of each iteration. Alternatively, if you have a list of the data.frame()s, you can just pass that to lapply and drop the "get" call. Does that help? Sorry if not -- I had a little bit of trouble deciphering your code. Michael On Tue, Jan 24, 2012 at 7:08 PM, dthomas <dyfed.tho...@midlandshn.health.nz> wrote: > Hi all, > > I want to loop through a series of data frames and append them into one data > frame, however I do not want all columns of the original data frames to be > in the new data frame. I have the following code: > > phList<-c('ph2010','ph2009','ph2008','ph2007','ph2006') #Name of original > data frames > > for (i in phList) { > > x<-c(paste(i,"$ID",sep=""),paste(i,"$DATE_DISPENSED",sep=""),paste(i,"$TG_NAME1",sep=""), > paste(i,"$TG_NAME2",sep=""),paste(i,"$TG_NAME3",sep="")) # I may be over > complicating things here!? > > phNew<-rbind(phNew,(data.frame(ID=get(x[1]), DATE_DISPENSED=get(x[2]), > TG_NAME1= get(x[3]), TG_NAME2=get(x[4]), TG_NAME3=get(x[5])))) > } > > The error i get is that the columns for extration are not recognised as > objects which i understand. What i need resolving is how do i get around > this so that each column desired is extracted from the original data frames? > Is there a way to make the string (where my over complicating note is) of > the column name into the column name as get() does not work as I have it. > > Your help is much appreciated, > D > > -- > View this message in context: > http://r.789695.n4.nabble.com/Converting-strings-into-data-frame-column-names-tp4325870p4325870.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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.