Metadata for oligo bioconductor package

Question

[Bio]

So I am going through the oligo User guide (see: https://www.bioconductor.org/packages/release/bioc/vignettes/oligo/inst/doc/oug.pdf) and I encountered this unfinished line on page 12:

metadata <- data.frame(labelDescription=c('wafer', 'experiment', 'complex'), channel=factor

I was wondering what else is supposed to be on this line? Am I just suppose to close the parentheses or should there be other information here?

Thank you!

[Basti]

There is an issue with pdf viewer, the complete line is : metadata <- data.frame(labelDescription=c('wafer', 'experiment', 'complex'), channel=factor('_ALL_'))