Thank you Michael. One follow up question: In the solution using apply(), why are we feeding x[2] inside testfun instead of x[[2]]? Aren't we supposed to feed the vector of values to the function, which is achieved by x[[2]]?
Thnks. On Sat, Jun 9, 2012 at 3:38 PM, R. Michael Weylandt <michael.weyla...@gmail.com> wrote: > No worries -- it's an important question and it introduces you to one > of the most important R idioms. [And you get bonus points for having a > well formed question!] > > You're probably looking for something like this: > > apply(testframe, 1, function(x) testfun(x[2])) > > Which goes row-by-row and substitutes the second element (your col2) > into testfun leaving the y= unsupplied and hence defaulting to 2. This > seems a little kludgy, however, in light of the below. (Also, if you > have a data frame of multiple types, it seems to get in trouble > quicker than I would have imagined) > > Note that this is not particularly efficient and you could just use > > testfun(testframe[["col2"]]) > > instead using the magic of vectorization. Very rarely do you need to > do things "one-by-one" except for recursive/state-dependent > simulations. > > Best, > Michael > > On Sat, Jun 9, 2012 at 9:12 AM, Onur Uncu <onuru...@gmail.com> wrote: >> Apologees the novice question. Currently climbing up the learning curve of R. >> >> Suppose I have the following function and the data.frame: >> >> testfun<-function(x=1,y=2) x+y >> >> testframe=data.frame(col1=c(1,2),col2=c(3,4)) >> >> When evaluating testfun, I want to use the default value for y (which >> is 2) and for x, I want to feed (one by one) the values in col2 of >> testframe. How can I achieve this please? Not having much success with >> apply() >> >> Thanks for any help. >> >> ______________________________________________ >> 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.
