purrrogress

The goal of purrrogress is to add as simply as possible progress bars to purrr mapping functions.

Installation

You can install the released version of purrrogress from CRAN with:

install.packages("purrrogress")

Using

Progress bars can be added to any map function with the with_progress() function wrapped around the function to be mapped.

library(purrrogress)
## basic example code

fun <- function(...){
    # this does nothing but take time.
    Sys.sleep(0.1)
    invisible(NULL)
}
invisible(map(1:100, with_progress(fun)))

This example doesn’t do much but illustrates the simplicity of purrrogress bars. The length of the progress bar is imputed from the variable passed to the map function as well as the title and label for the progress bar. No changes are needed to the function and all arguments are passed on as is.

Caveat

The with_progress() function can only impute the length if it is actually part of the map call. The following will not work.

# This will not work.
not_so_fun <- with_progress(fun)
invisible(map(1:100, not_so_fun))

This could be made to work by specifying the length if known a priori.

# The fix
just_less_fun <- with_progress(fun, 100)
invisible(map(1:100, just_less_fun))

Directly

The progress bars used by purrrogress are defined in a class system described in a later section. Progress bars can be created and manipulated directly through the progress_bar() function.

pb <- progress_bar(100, "A Title", "An informative label", type="none")

The type argument will determine what type of progress bar is created, windows, Tk, or none(used for testing and demonstration).

Customization

The progress bar windows can be customized to display relevant information such as the number of elements completed, or the estimated time remaining. This can be accomplished through inserting glue style keywords. These keywords are added by default:

• total - the total number of elements.
• current - the current number of elements completed.
• frac - an alias for "{current}/{total}", giving the nicely formatted fraction of completed elements.
• percent - the percent completed as a whole number percent.
• elapsed.time - The total time elapsed from the start to the completion of the last step() or update() call, typically the last element completion.
• average.time - The average time to complete each step.
• estimated.total.time - a naive estimate of the total time remaining. Taken as the average.time * total.
• estimated.time.remaining - Just what is says, estimated.total.time - elapsed.time.
• etr - alias for estimated.time.remaining

These keywords can be used in either the title or the label of progress bars to obtain more informative messages.

pb <- progress_bar( 100
                  , title = "Test progress bar ({etr})"
                  , label = "{frac}({percent}) completed."
                  , initial = 50
                  )
pb$init()
Sys.sleep(2)
pb$title
#> Test progress bar (00:00:02)
pb$label
#> 50/100(50%) completed.
pb$term()

Adding Bindings

In addition to those provided, additional bindings can be added to show even more information.

words <- stringi::stri_rand_lipsum(1, FALSE) %>%
         stringi::stri_split(fixed = ' ') %>%
         unlist()
pb <- R6_progress$new( length(words)
                     , title = "Test Progress {current}/{total}"
                     , label = "Working on item {current}, {word}"
                     , bindings = list(word = ~words[pb$current+1])
                     )
pb$init()
pb$label
#> Working on item 0, Maecenas
pb$step()
pb$label
#> Working on item 1, ac
pb$step()
pb$label
#> Working on item 2, eget
pb$term()

Class System

Additional progress bars may be defined to work within the purrrogress framework, however each must inherit from the base progress class, “R6 Progress Base Class” which handles the creation and management of the active bindings for titles and labels.

Public Methods to Implement.

The following are public methods for which a derived class must implement.

• init() - This is called at the beginning of a loop or apply function. It should contain the code to actually create and show the progress bar window. Variables that are used to monitor and control the progress windows through other steps should be initialized here. It should additionally call super$init() to start timers. The return value should be invisible(self).
• term() - This is called to close any open windows, close connections and free resources. After term() is called the progress object should be unusable. There is no need to call super$term() at this time but is it provided for good practice. The return value is expected to be invisible(NULL).
• update(...) - This takes any number of arguments which may be used to update internal variables or displays. This should handle updating of the progress window, titles, labels, etc. The return value is expected to be invisible(self).

Other Public Methods

The following are functions that are provided in the public interface for R6 progress bars but do not need to be implemented in child classes, or when implemented care should be taken to carry forward the default behavior.

• step(n=1L, ..., keep.open=FALSE) - This is called to increment the internal progress counter, it in turn calls update(...) function the update any windows, titles and labels. The n argument is provided to allow for taking uneven steps. The keep.open argument is provided to allow for windows that stay open to show relevant information, such as total time or average time per step. If keep.open is false (default) when the current counter reaches the total term() will be called.
• initialize(...) - populates the initial values of title, label, and initial count, which cannot be changed once specified.
• add_binding() - adds an active binding which may be used in the title or label.
• add_bindings(...) - a more convenient way to specify multiple bindings at once in the form of add_bindings(name=funtion(){...}).
• expose(sym) - The most convenient way of binding variable to use in the title or label. When called the variable from the current scope is added to the available bindings so that it may be referenced in the title or label.

Acknowledgements

This project was inspired by a post to R-Bloggers by Adi Sarid. Credit goes to him for the original idea on which purrrogress is built.