bookdown + exams + webex

First and foremost, the main part of the hack is to realize that any exercises in a .Rmd file can be broken into a list using exams::xexams. Let’s use an example from the book, with the first three exercises of chapter 01:

# example from book 
afedR::copy_book_files(path_to_copy = tempdir())
## Copying data files files to /tmp/RtmpIs4EpM/afedR files/data
##  37 files copied
## Copying end-of-chapter (eoc) exercises with solutions to /tmp/RtmpIs4EpM/afedR files/eoc-exercises/
##  99 files copied
## Copying R code to /tmp/RtmpIs4EpM/afedR files/R-code
##  15 files copied
# temp folder with exercises
eoc_dir <- file.path(tempdir(), 'afedR files/eoc-exercises/')

# select exercises
my_exercises <- list.files(eoc_dir, pattern = '*.Rmd', full.names = TRUE)
my_exercises <- my_exercises[1:3]

# break it down
my_l <- exams::xexams(my_exercises)

# check it
dplyr::glimpse(my_l)
## List of 1
##  $ exam1:List of 3
##   ..$ exercise1:List of 6
##   .. ..$ question    : chr [1:3] "" "The R language was developed based on what other programming language?" ""
##   .. ..$ questionlist: chr [1:5] "C++" "Python" "Julia" "Javascript" ...
##   .. ..$ solution    : chr [1:2] "" "Straight from the book, section **What is R**: \"R is a modern version of S, a programming language originally "| __truncated__
##   .. ..$ solutionlist: NULL
##   .. ..$ metainfo    :List of 18
##   .. ..$ supplements : Named chr(0) 
##   .. .. ..- attr(*, "names")= chr(0) 
##   .. .. ..- attr(*, "dir")= chr "/tmp/RtmpIs4EpM/file4e094f974499/exam1/exercise1"
##   ..$ exercise2:List of 6
##   .. ..$ question    : chr [1:3] "" "What are the names of the two authors of R?" ""
##   .. ..$ questionlist: chr [1:5] "Linus Torvalds and Richard Stallman" "John Chambers and Robert Engle" "Roger Federer and Rafael Nadal" "Guido van Rossum and Bjarne Stroustrup" ...
##   .. ..$ solution    : chr [1:3] "" "Straight from the book: \"... The base code of R was developed by two academics, **Ross Ihaka** and **Robert Ge"| __truncated__ ""
##   .. ..$ solutionlist: NULL
##   .. ..$ metainfo    :List of 18
##   .. ..$ supplements : Named chr(0) 
##   .. .. ..- attr(*, "names")= chr(0) 
##   .. .. ..- attr(*, "dir")= chr "/tmp/RtmpIs4EpM/file4e094f974499/exam1/exercise2"
##   ..$ exercise3:List of 6
##   .. ..$ question    : chr [1:4] "" "Why is R special when comparing to other programming languages, such as Python, C++, javascript and others?" "" ""
##   .. ..$ questionlist: chr [1:5] "It was designed for analyzing data and producing statistical output" "Easy to use" "Works on any plataform such as Windows, Unix, MacOS" "Makes it easy to write mobile apps" ...
##   .. ..$ solution    : chr [1:2] "" "Undoubtedly, the main differential of the R language is the ease with which data can be analyzed on the platfor"| __truncated__
##   .. ..$ solutionlist: NULL
##   .. ..$ metainfo    :List of 18
##   .. ..$ supplements : Named chr(0) 
##   .. .. ..- attr(*, "names")= chr(0) 
##   .. .. ..- attr(*, "dir")= chr "/tmp/RtmpIs4EpM/file4e094f974499/exam1/exercise3"

As an example, in this list you can see the main text of the question 01 in slot l_out$exam1$exercise1$question:

my_l$exam1$exercise1$question
## [1] ""                                                                      
## [2] "The R language was developed based on what other programming language?"
## [3] ""

And the solution at my_l$exam1$exercise1$solution

my_l$exam1$exercise1$solution
## [1] ""                                                                                                                                                                                       
## [2] "Straight from the book, section **What is R**: \"R is a modern version of S, a programming language originally created in Bell Laboratories (formerly AT&T, now Lucent Technologies).\""

In my case, I wanted the html version of the book to have all the solutions hidden by a clickable button – just like in webex – while the pdf and ebook would only have the text of the questions. Here are the functions I used:

compile_eoc_exercises <- function(files_in, type_doc) {
  my_counter <<- 1

  if (is.null(type_doc)) {
    type_doc = 'html'
    #type_doc = 'latex'
  }

  for (i_ex in files_in) {
    exercise_to_html(i_ex, my_counter = my_counter,
                     type_doc)

    my_counter <<- my_counter +1
  }

  return(invisible(TRUE))
}

exercise_to_html <- function(f_in, my_counter, type_doc) {

  require(exams)
  require(webex)
  require(tidyverse)

  text_pre_solution <- paste0('To reach the same result, you must execute the code below. ',
                           'For that, open a new R script in RStudio (Control+shift+N), ',
                           'copy and paste the code, and execute it whole by pressing ',
                           'Control+Shift+Enter or line by line with shortcut ',
                           'Control+Enter.')

  my_dir <- file.path(tempdir(), basename(tempfile()))
  dir.create(my_dir)

  suppressMessages({
  l_out <- exams::xexams(f_in, driver = list(sweave = list(png = TRUE)),
                         dir = my_dir)

  })

  exercise_text <- paste0(l_out$exam1$exercise1$question, collapse = '\n')
  alternatives <- l_out$exam1$exercise1$questionlist
  correct <- l_out$exam1$exercise1$metainfo$solution
  solution <- paste0(l_out$exam1$exercise1$solution,
                     collapse = '\n')
  ex_type <- l_out$exam1$exercise1$metainfo$type

  if (type_doc %in% c('latex', 'epub3')) {

    my_str <- str_glue('\n\n {sprintf("%02d", my_counter)} - {exercise_text} \n\n ')

    if (ex_type == 'schoice') {
      n_alternatives <- length(alternatives)

      for (i_alt in seq(1, n_alternatives)) {
        my_str <- paste0(my_str,
                         letters[i_alt],') ', alternatives[i_alt],
                         '\n')
      }

    }

    cat(my_str)

    return(invisible(TRUE))

  } else if (type_doc == 'html') {

    if (ex_type == 'schoice') {
      vec_mcq <- sample(
        c(alternatives[!correct],
          answer = alternatives[correct])
      )

      my_answers_text <- str_glue('<br> Solution: {mcq(vec_mcq)}')
      numeric_sol <- alternatives[correct]
      text_sol <- str_glue('The solution is {numeric_sol}. {text_pre_solution}')

    } else if (ex_type == 'num') {

      numeric_sol <- correct
      my_answers_text <- str_glue('<br><br> Your Answer: {fitb(correct)}')
      text_sol <- str_glue('The solution is {numeric_sol}. {text_pre_solution}')

    } else if (ex_type == 'string') {
      my_answers_text <- ''
      numeric_sol <- ''

      if (stringr::str_detect(solution,
                              '```text')) {
        text_sol <- paste0('In order to execute the code, open a new R script in RStudio (Control+shift+N), ',
                           'copy and paste the code, and execute it whole by pressing ',
                           'Control+Shift+Enter or line by line with shortcut ',
                           'Control+Enter.')

      } else {
        text_sol <- ''
      }

    }

    my_str <- paste0('\n\n <hr> \n',
                     webex::total_correct(), '\n',
                     '### Q.', my_counter, '{-} \n',
                     exercise_text, '\n',
                       my_answers_text)

    temp_id <- basename(tempfile(pattern = 'collapse_'))
    sol_str <- str_glue(
      ' <div style="text-align: left; margin-top: 2px; padding: 13px 0 10px 0;"><p><button class="btn btn-primary" type="button" data-toggle="collapse" data-target="#{temp_id}" aria-expanded="false" aria-controls="collapseExample">
    Solution
  </button> </p> </div>

<div class="collapse" id="{temp_id}">
{text_sol}
  <div class="card card-body">
    {solution}
  </div>
</div>')

    cat(paste0(my_str, '\n' ,
               sol_str))

  }

  return(invisible(TRUE))

}

compile_eoc_exercises(my_exercises, type_doc = 'html')

compile_eoc_exercises(my_exercises, type_doc = 'latex')

Conclusion

Its is amazing how much we can accomplish by learning and mixing different technologies. In this case, I used R, Latex, html, javascript and css to bundle reproducible and dynamic exercises for my book. You can find examples of the final output in html, pdf and ebook.

If you’re trying it for you own book, make sure to add the correct .js and .css files to the html compilation. In my case, I used my_javascript.js and style_html.css.