How to merge two strings

Claus Hindsgaul wrote:

Thank you all!
Paste() was just the function I needed to know!

 Or sprintf:

 > s1 <- "R-"
 > s2 <- "project"
 > sprintf("%s%s",s1,s2)

 [1] "R-project"

 It seems to be much faster:

 > unix.time(for(i in 1:100000){junk=sprintf("%s%s",s1,s2)})

 [1] 1.12 0.00 1.12 0.00 0.00

 > unix.time(for(i in 1:100000){junk=paste(s1,s2,sep='')})

 [1] 5.90 0.01 5.92 0.00 0.00

 Not that I imagine string concatenation will ever be a bottleneck
worth optimising but there it is. A well-constructed sprintf() call may
be more readable than a pastey mess though, with all its fiddly commas
and quotes - contrived example:

 > sprintf("%s://%s%s/%s",scheme,host,dir,file)

 [1] "http://www.foo.com/foo/bar/baz.txt"

 > paste(scheme,'://',host,dir,'/',file,sep='')

 [1] "http://www.foo.com/foo/bar/baz.txt"

 which do you prefer?