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

> ### Name: act
> ### Title: Aligned Corpus Toolkit
> ### Aliases: act
> 
> ### ** Examples
> 
> library(act)
> 
> # ========== Example data 
> # The act package comes with some example data. 
> # The data is stored at the following location:
> path <- system.file("extdata", "examplecorpus", package="act")
> 
> # Since this folder is quite difficult to access, you might consider copying the 
> # contents of this folder to a more convenient location.
> # The following commands will create a new folder called 'examplecorpus' in the
> # folder 'path'.
> # You will find the data there.
> ## Not run: 
> ##D path <- "EXISTING_FOLDER_ON_YOUR_COMPUTER"
> ##D sourcepath <- system.file("extdata", "examplecorpus", package="act")
> ##D if (!dir.exists(path)) {dir.create(path)}
> ##D file.copy(sourcepath, dirname(path), recursive=TRUE)
> ## End(Not run)
> 
> # The example files that come with the package do only contain annotation files.
> # Media files are not included.
> # The following lines will download the data and create a new folder called 
> # 'examplecorpus' in the folder 'path'.  
> # You will find the data there.
> ## Not run: 
> ##D path <- "EXISTING_FOLDER_ON_YOUR_COMPUTER"
> ##D sourceurl <- 
> ##D "http://www.romanistik.uni-freiburg.de/ehmer/files/digitalhumanities/act_examplecorpus.zip"
> ##D temp <- tempfile()
> ##D download.file(sourceurl, temp)
> ##D unzip(zipfile=temp, exdir=path)
> ## End(Not run)
> 
> # ========== Create a corpus object and load data
> # Now that we have the example data accessible, we can create a corpus object.
> # The corpus object is a structured collection of all the information that you can 
> # work with using act.
> # It will contain the information of each transcript, links to media files and further 
> # meta data.
> 
> # --- Locate folder with annotation files
> # When creating a corpus object you will need to specify where your annotation 
> # files ('Praat' '.TextGrids' or 'ELAN' .eaf) are located.
> # We will use the example data, that we have just located in 'path'.
> path
[1] "D:/temp/Rtmp6DOwLg/RLIBS_12ec035627493/act/extdata/examplecorpus"
> 
> # In case that you want to use your own data, you can set the path here:
> ## Not run: 
> ##D 	path <- "EXISTING_FOLDER_ON_YOUR_COMPUTER"
> ## End(Not run)
> 
> # --- Create corpus object and load annotation files
> # The following command will create a corpus object, with the name 'examplecorpus'.
> examplecorpus <- act::corpus_new(
+ 	pathsAnnotationFiles = path,
+ 	pathsMediaFiles = path,
+ 	name = "examplecorpus"
+ )
Warning in `[<-.factor`(`*tmp*`, is.na(tiers$tier.parent.ref), value = 1) :
  invalid factor level, NA generated
Error in Ops.factor(annotations$tier, all_tiers[i]) : 
  level sets of factors are different
Calls: <Anonymous> ... <Anonymous> -> <Anonymous> -> <Anonymous> -> which -> Ops.factor
Execution halted