ROBUSTNESS: Add explicit 'stringsAsFactors' arguments [data.frame]

[HenrikBengtsson]

$ for pkg in $pkgs; do echo "$pkg:"; (cd "$pkg"; grep -E "^[ \t]*[^#].*data[.]frame" -- */*.R | grep -vF stringsAsFactors;); echo; read -r -p "Press ENTER to continue ..."; done

future.tests:
R/check_plan.R:     sets_of_args <- as.data.frame(defaults)
R/Test-class.R:as.data.frame.Test <- function(x, ..., expand = TRUE, arg_names = NULL) {
R/Test-class.R:    args <- data.frame(args = I(list(args)))
R/Test-class.R:  if (is.data.frame(args)) {
R/Test-class.R:  df <- lapply(args, FUN = as.data.frame, ...)
R/Test-class.R:  ## Expand all data.frame:s to have the same set of columns
R/Test-class.R:  ## Reduce to one data.frame
R/TestResult-class.R:as.data.frame.TestResult <- function(x, ..., arg_names = NULL) {
R/TestResult-class.R:  df <- lapply(args, FUN = as.data.frame, ...)
R/TestResult-class.R:  ## Expand all data.frame:s to have the same set of columns
R/TestResult-class.R:  ## Reduce to one data.frame