R: Add a progress bar to a mapping function or for loop

cli_progress_along {cli}

R Documentation

Add a progress bar to a mapping function or for loop

Description

Note that this function is currently experimental!

Use cli_progress_along() in a mapping function or in a for loop, to add a progress bar. It uses cli_progress_bar() internally.

Usage

cli_progress_along(
  x,
  name = NULL,
  total = length(x),
  ...,
  .envir = parent.frame()
)

Arguments

`x`	Sequence to add the progress bar to.
`name`	Name of the progress bar, a label, passed to `cli_progress_bar()`.
`total`	Passed to `cli_progress_bar()`.
`...`	Passed to `cli_progress_bar()`.
`.envir`	Passed to `cli_progress_bar()`.

Details

`for` loop

A for loop with cli_progress_along() looks like this:

for (i in cli_progress_along(seq)) {
  ...
}

A complete example:

clifun <- function() {
  for (i in cli_progress_along(1:100, "Downloading")) {
     Sys.sleep(4/100)
  }
}
clifun()

`lapply()` and other mapping functions

They will look like this:

lapply(cli_progress_along(X), function(i) ...)

A complete example:

res <- lapply(cli_progress_along(1:100, "Downloading"), function(i) {
  Sys.sleep(4/100)
})

Custom format string

clifun <- function() {
  for (i in cli_progress_along(1:100,
      format = "Downloading data file {cli::pb_current}")) {
     Sys.sleep(4/100)
  }
}
clifun()

Breaking out of loops

Note that if you use break in the for loop, you probably want to terminate the progress bar explicitly when breaking out of the loop, or right after the loop:

for (i in cli_progress_along(seq)) {
  ...
  if (cond) cli_progress_done() && break
  ...
}

Value

An index vector from 1 to length(x) that triggers progress updates as you iterate over it.