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

> ### Name: vpc_cat
> ### Title: VPC function for categorical
> ### Aliases: vpc_cat
> 
> ### ** Examples
> 
> 
> ## See vpc.ronkeizer.com for more documentation and examples
> library(vpc)
> 
> # simple function to simulate categorical data for single individual
> sim_id <- function(id = 1) {
+   n <- 10
+   logit <- function(x) exp(x) / (1+exp(x))
+   data.frame(id = id, time = seq(1, n, length.out = n),
+              dv = round(logit((1:n) - n/2 + rnorm(n, 0, 1.5))) )
+ }
> ## simple function to simulate categorical data for a trial
> sim_trial <- function(i = 1, n = 20) { # function to simulate categorical data for a trial
+   data.frame(sim = i, do.call("rbind", lapply(1:n, sim_id)))
+ }
> 
> ## simulate single trial for 20 individuals
> obs <- sim_trial(n = 20)
> 
> ## simulate 200 trials of 20 individuals
> sim <- do.call("rbind", lapply(1:200, sim_trial, n = 20))
> 
> ## Plot categorical VPC
> vpc_cat(sim = sim, obs = obs)
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: vpc_cat ... tryCatch -> tryCatchList -> tryCatchOne -> <Anonymous>
Execution halted