Install Package Dependencies in R

install_dep.R

#' Install Dependent Packages
#'
#' @param pkg.dir refers to the package directory that contains the 
#'     \code{Description} file
#' @param dependencies defines which dependencies of the dependent packages are 
#'     to be installed
#' @param repos is the (CRAN) repository used to install dependencies
#' @param lib is the library to which packages are installed
install_dep = function(pkg.dir = ".", dependencies = TRUE, repos = getOption("repos")[1], lib = .libPaths()[1]) {
    
    # default dependencies
    if(dependencies == TRUE) {
        dependencies = c("Depends", "Imports", "LinkingTo")
    }
    
    # returns string w/o leading or trailing whitespace
    trim = function (x) gsub("^\\s+|\\s+$", "", x)
    
    # http://stackoverflow.com/questions/30223957/elegantly-extract-r-package-dependencies-of-a-package-not-listed-on-cran
    dcf = read.dcf(file.path(pkg.dir, "DESCRIPTION"))
    deps = unique(gsub("\\s.*", "", trim(unlist(strsplit(dcf[, intersect(dependencies, colnames(dcf))], ","), use.names = FALSE))))
    
    # install dependencies that aren't already installed
    deps = deps[!(deps %in% c("R", rownames(installed.packages())))]
    if(length(deps) > 0) {
        message(paste("Also installing:", paste(deps)))
        install.packages(deps)
    }
}