Add the 'with_wd' function originally written by Tyler Smith, with an…

… example added by Leo to form a complete unit at https://github.com/LieberInstitute/sgejobs/blob/devel/R/utils.R

Co-authored-by: Leonardo Collado Torres <[email protected]>

R/utils.R

@@ -0,0 +1,27 @@
+#' Temporarily evaluate an expression in a directory
+#'
+#' Temporarily evaluate an expression in a directory, then set the directory
+#' back to the original.
+#'
+#' @param dir a directory to perform an expression within.
+#' @param expr expression to evaluate.
+#'
+#' @details See here: http://plantarum.ca/code/setwd-part2/
+#' @export
+#' @author Tyler Smith, contributed to regionReport by David Robinson
+#' https://github.com/dgrtwo
+#'
+#' @examples
+#'
+#' ## Create a directory called 'hola' and then check that it exists
+#' with_wd(tempdir(), {
+#'     dir.create("hola", showWarnings = FALSE)
+#'     file.exists("hola")
+#' })
+#'
+with_wd <- function(dir, expr) {
+    wd <- getwd()
+    on.exit(setwd(wd))
+    setwd(dir)
+    eval(expr, envir = parent.frame())
+}