progress: Display progression of a long calculation at the R console and/or in a GUI

Description

Display progression level of a long-running task in the console. Two mode can be used: either percent of achievement (55%), or the number of items or steps done on a total (1 file on 10 done...). This is displayed either through a message, or through a text-based "progression bar" on the console, or a true progression bar widget in a GUI.

Usage

progress(value, max.value = NULL, progress.bar = FALSE, char = "|",
  init = (value == 0), console = TRUE, gui = TRUE)

Arguments

value

Current value of the progression (use a value higher than max.value to dismiss the progression indication automatically.

max.value

Maximum value to be achieved.

progress.bar

Should we display a progression bar on the console? If FALSE, a temporary message is used.

char

The character to use to fill the progress bar in the console. not used for the alternate display, or for GUI display of progression.

init

Do we have to initialize the progress bar? It is usually done the first time the function is used, and the default value init = (value == 0) is correct most of the time. You must specify init = TRUE in two cases: (1) if the first value to display is different from zero, and (2) if your code issues some text on screen during progression display. Hence, you must force redraw of the progression bar.

console

Do we display progression on the console?

gui

Do we display progression in a dialog box, or any other GUI widget? See "details" and "examples" hereunder to know how to implement your own GUI progression indicator.

Value

This function returns NULL invisibly. It is invoked for its side effects.

Details

The function progress() proposes different styles of progression indicators than the standard txtProgressBar() in package 'utils'.

The function uses backspace (\8) to erase characters at the console.

With gui = TRUE, it looks for all functions defined in the .progress list located in the SciViews:TempEnv environment. Each function is executed in turn with following call: the_gui_function(value, max.value). You are responsible to create the_gui_function() and to add it as an element in the .progress list. See also example (5) hereunder.

If your GUI display of the progression offers the possibility to stop calculation (for instance, using a 'Cancel' button), you are responsible to pass this info to your code doing the long calculation and to stop it there. Example (5) shows how to do this.

Examples

Run this code

# NOT RUN {
# 1) A simple progress indicator in percent
for (i in 0:101) {
  progress(i)
  Sys.sleep(0.01)
  if (i == 101) message("Done!")
}

# 2) A progress indicator with 'x on y'
for (i in 0:31) {
  progress(i, 30)
  Sys.sleep(0.02)
  if (i == 31) message("Done!")
}

# 3) A progress bar in percent
for (i in 0:101) {
  progress(i, progress.bar = TRUE)
  Sys.sleep(0.01)
  if (i == 101) message("Done!")
}

# 4) A progress indicator with 'x on y'
for (i in 0:21) {
  progress(i, 20, progress.bar = TRUE)
  Sys.sleep(0.03)
  if (i == 21) message("Done!")
}

# 5) A progression dialog box with Tcl/Tk
# }
# NOT RUN {
if (require(tcltk)) {
  gui_progress <- function(value, max.value) {
    # Do we need to destroy the progression dialog box?
    if (value > max.value) {
      try(tkdestroy(get_temp("gui_progress_window")), silent = TRUE)
      delete_temp(c("gui_progress_state", "gui_progress_window",
        "gui_progress_cancel"))
      return(invisible(FALSE))
    } else if (exists_temp("gui_progress_window") &&
      !inherits(try(tkwm.deiconify(tt <- get_temp("gui_progress_window")),
        silent = TRUE), "try-error")) {
      # The progression dialog box exists
      # Focus on it and change progress value
      tkfocus(tt)
      state <- get_temp("gui_progress_state")
      tclvalue(state) <- value
    } else {
      # The progression dialog box must be (re)created
      # First, make sure there is no remaining "gui_progress_cancel"
      delete_temp("gui_progress_cancel")
      # Create a Tcl variable to hold current progression state
      state <- tclVar(value)
      assign_temp("gui_progress_state", state)
      # Create the progression dialog box
      tt <- tktoplevel()
      assign_temp("gui_progress_window", tt)
      tktitle(tt) <- "Waiting..."
      sc <- tkscale(tt, orient = "h", state = "disabled", to = max.value,
        label = "Progress:", length = 200, variable = state)
      tkpack(sc)
      but <- tkbutton(tt, text = "Cancel", command = function() {
        # Set a flag telling to stop running calculation
        assign_temp("gui_progress_cancel", TRUE) # Content is not important!
        tkdestroy(tt)
      })
      tkpack(but)
    }
    invisible(TRUE)
  }
  # Register it as function to use in progress()
  change_temp(".progress", "gui_progress", gui_progress,
    replace.existing = TRUE)
  rm(gui_progress) # Don't need this any more
  # Test it...
  for (i in 0:101) {
    progress(i) # Could also set console = FALSE for using the GUI only
    Sys.sleep(0.05)
    # The code to stop long calc when user presses "Cancel"
    if (exists_temp("gui_progress_cancel")) {
      progress(101, console = FALSE) # Make sure to clean up everything
      break
    }
    if (i == 101) message("Done!")
  }
  # Unregister the GUI for progress
  change_temp(".progress", "gui_progress", NULL)
}
# }