Running examples in 'exams-Ex.R' failed
The error most likely occurred in:

> ### Name: read_exercise
> ### Title: Reading LaTeX/Markdown Exercise Files
> ### Aliases: read_exercise extract_command extract_extra
> ###   extract_environment extract_items read_metainfo
> ### Keywords: utilities
> 
> ### ** Examples
> 
> ## xexams() uses read_exercise() by default to read in
> ## each individual exercise, e.g., here for only a single
> ## exam with only a single exercise the result is:
> set.seed(1090)
> xexams("tstat.Rnw")[[1]][[1]]
$question
[1] "A machine fills milk into $500$ml packages. It is suspected that the "       
[2] "machine is not working correctly and that the amount of milk filled differs "
[3] "from the setpoint $\\mu_0 = 500$. A sample of $226$ packages "               
[4] "filled by the machine are collected. The sample mean $\\bar{y}$ is equal to "
[5] "$517.2$ and the sample variance $s^2_{n-1}$ is equal to "                    
[6] "$262.56$."                                                                   
[7] ""                                                                            
[8] "Test the hypothesis that the amount filled corresponds on average to the "   
[9] "setpoint. What is the absolute value of the $t$~test statistic?"             

$questionlist
NULL

$solution
[1] "The $t$~test statistic is calculated by:"                        
[2] "\\begin{eqnarray*}"                                              
[3] "  t & = & \\frac{\\bar y - \\mu_0}{\\sqrt{\\frac{s^2_{n-1}}{n}}}"
[4] "  = \\frac{517.2 - 500}{\\sqrt{\\frac{262.56}{226}}}"            
[5] "  = 15.958."                                                     
[6] "\\end{eqnarray*}"                                                
[7] "The absolute value of the $t$~test statistic is thus equal to"   
[8] "$15.958$."                                                       

$solutionlist
NULL

$metainfo
$metainfo$file
[1] "tstat"

$metainfo$markup
[1] "latex"

$metainfo$type
[1] "num"

$metainfo$name
[1] "t statistic"

$metainfo$title
NULL

$metainfo$section
NULL

$metainfo$version
NULL

$metainfo$solution
[1] 15.958

$metainfo$tolerance
[1] 0.01

$metainfo$clozetype
NULL

$metainfo$points
NULL

$metainfo$time
NULL

$metainfo$shuffle
[1] FALSE

$metainfo$single
[1] FALSE

$metainfo$length
[1] 1

$metainfo$string
[1] "t statistic: 15.958 (15.948--15.968)"

$metainfo$maxchars
NULL

$metainfo$abstention
NULL


$supplements
named character(0)
attr(,"dir")
[1] "D:\\temp\\RtmpM7ppWl\\file165546d851afe/exam1/exercise1"

> 
> ## the corresponding Markdown version has:
> set.seed(1090)
> xexams("tstat.Rmd")[[1]][[1]]
Error in namespaceExport(ns, exports) : 
  undefined exports: %s!=%, %s!==%, %s+%, %s<%, %s<=%, %s==%, %s===%, %s>%, %s>=%, %stri!=%, %stri!==%, %stri+%, %stri<%, %stri<=%, %stri==%, %stri===%, %stri>%, %stri>=%, stri_datetime_add<-, stri_sub<-, stri_subset<-, stri_subset_charclass<-, stri_subset_coll<-, stri_subset_fixed<-, stri_subset_regex<-, stri_c, stri_c_list, stri_cmp, stri_cmp_eq, stri_cmp_equiv, stri_cmp_ge, stri_cmp_gt, stri_cmp_le, stri_cmp_lt, stri_cmp_neq, stri_cmp_nequiv, stri_compare, stri_conv, stri_count, stri_count_boundaries, stri_count_charclass, stri_count_coll, stri_count_fixed, stri_count_regex, stri_count_words, stri_datetime_add, stri_datetime_create, stri_datetime_fields, stri_datetime_format, stri_datetime_fstr, stri_datetime_now, stri_datetime_parse, stri_datetime_symbols, stri_detect, stri_detect_charclass, stri_detect_coll, stri_detect_fixed, stri_detect_regex, stri_dup, stri_duplicated, stri_duplicated_any, stri_enc_detect, stri_enc_detect2, stri_enc_fromutf32, stri_enc_get, stri_enc_inf
Calls: xexams ... tryCatch -> tryCatchList -> tryCatchOne -> <Anonymous>
Execution halted