I'll unpack it bit by bit: stringsAsFactors = FALSE is a command to tell R how to construct the data frame: this doesn't apply to you because you already have a data frame, but I need it to set up my examples. By default, when you give R data that looks like strings/labels, it wants to convert those to factors (category data), but this stops that behavior and keeps the characters. This is considered by many to be a bad default, but it's so fundamental to the language that it couldn't be changed now without breaking lots of code. Perhaps something we'll see in an R 3.0 if that ever happens.
lapply(countries, function(x) x %in% euro) -- function(x) x%in% euro simply checks for each x which elements are in the european union and returns logical (True/False) values -- the lapply call goes column by column (here just the two in my example) because data.frames are really lists and each column is a list element. This latter point is somewhat subtle so don't worry too much about it just yet -- I could have done apply(, 2, ) and it would be just as good. Reduce -- takes a list of arguments and combines them sequentially with another function, here `&` (the AND function) -- For instance, a sum function could be written as Reduce(`+`, inputs) e.g., Reduce(`+`, list(1,2,3,4)) = 1 + Reduce(`+`, list(2,3,4)) = 1 + 2 + Reduce(`+`, list(3,4)) = 3 + 3 + Reduce(`+`, list(4)) = 6 + 4 = 10 -- for this example, it checks all the countries (just two columns) and ANDs them (per your request) cbind -- attaches a new column dput simply converts an object to plain text so it can be emailed easily -- the console printout doesn't give enough information for us to reproduce your problem/data, but dput will. It's not specific to your problem -- just a mailing list / reproducibility hint. Hope this helps, Michael On Wed, Apr 18, 2012 at 2:24 AM, phillip03 <phillipbrig...@hotmail.com> wrote: > Wow it works :) Thank you SO much!! > I am very new at R and was thinking if you would explain what these to codes > do: > > countries<-data.frame(country1,country2,stringsAsFactors=FALSE) > > # I know this i a vector with both my county lists but what does > stringsAsFacors= FALSE do ?. What if I wantede a row with 1=TRUE and 0=FALSE > > and > > > cbind(countries,EMU=Reduce(`&`, lapply(countries, > + function(x) x %in% euro))) > > # here I columnbind my new defined vector and produce a new one ? What does > the Reduce and lapply do ? > > > I am also not quite sure of the dput() you wrote michael sorry. I understand > if you dont have the time to help further :) > > Ph > > -- > View this message in context: > http://r.789695.n4.nabble.com/How-to-add-specific-column-to-data-set-tp4565341p4566822.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.
