Install R-devel on Windows

rdevel.R

# check for and remove previous R-devel install
g <- getwd()
setwd(R.home())
setwd("../")
if("R-devel") %in% dir()) {
    setwd("R-devel")
    shell.exec(dir()[grep("unin.+exe$", dir())])
    ## walk through uninstall dialog
    setwd("../")
}

# download R-devel
tf <- file.path(tempdir(), "R-devel-win.exe")
d <- download.file("http://cran.r-project.org/bin/windows/base/R-devel-win.exe", tf, mode = "wb")
stopifnot(d == 0)

# run install wizard
shell.exec(tf)
## walk through install dialog

# copy packages from current install to r-devel
p <- c("devtools", "plyr", "knitr")
sapply(p, function(x) {
    if(!dir.exists(file.path("R-devel", "library", x))) {
        dir.create(file.path("R-devel", "library", x))
        file.copy(file.path(R.home(), "library", x), file.path("R-devel", "library"), recursive = TRUE)
    } else {
        FALSE
    }
})