Create a progress bar to be used with for loops that can possibly take a lot of time.
progress_bar(iter, total, start, message = NULL, width = 20)format_hms(seconds)
format_hms() returns a character in the hh:mm:ss format. progress_bar()
prints the progress bar on the console, calling cat(), therefore as returns
an invisible NULL.
integer. The current iteration step of the for loop.
integer. The total number of iterations.
POSIXct. The start time, as returned by Sys.time().
character. A message appearing before the progress bar.
integer. The length of the progress bar.
integer. Seconds to be converted into hh:mm:ss format.