Error(s) in re-building vignettes:
--- re-building 'tf_idf.Rmd' using rmarkdown

Attaching package: 'dplyr'

The following objects are masked from 'package:stats':

    filter, lag

The following objects are masked from 'package:base':

    intersect, setdiff, setequal, union

`summarise()` ungrouping output (override with `.groups` argument)
Joining, by = "book"
`stat_bin()` using `bins = 30`. Pick better value with `binwidth`.
Warning: Removed 896 rows containing non-finite values (stat_bin).
Warning: Removed 6 rows containing missing values (geom_bar).
--- finished re-building 'tf_idf.Rmd'

--- re-building 'tidying_casting.Rmd' using rmarkdown
Loading required package: NLP

Attaching package: 'NLP'

The following object is masked from 'package:ggplot2':

    annotate


Attaching package: 'dplyr'

The following objects are masked from 'package:stats':

    filter, lag

The following objects are masked from 'package:base':

    intersect, setdiff, setequal, union

Quitting from lines 122-127 (tidying_casting.Rmd) 
Error: processing vignette 'tidying_casting.Rmd' failed with diagnostics:
length(class) == 1L is not TRUE
--- failed re-building 'tidying_casting.Rmd'

--- re-building 'tidytext.Rmd' using rmarkdown

Attaching package: 'dplyr'

The following objects are masked from 'package:stats':

    filter, lag

The following objects are masked from 'package:base':

    intersect, setdiff, setequal, union

Joining, by = "word"
Joining, by = "word"
Joining, by = "word"
Joining, by = "word"
Loading required package: RColorBrewer

Attaching package: 'reshape2'

The following object is masked from 'package:tidyr':

    smiths

Joining, by = "word"
`summarise()` ungrouping output (override with `.groups` argument)
`summarise()` regrouping output by 'book' (override with `.groups` argument)
Joining, by = "word"
`summarise()` regrouping output by 'book' (override with `.groups` argument)
Selecting by ratio
--- finished re-building 'tidytext.Rmd'

SUMMARY: processing the following file failed:
  'tidying_casting.Rmd'

Error: Vignette re-building failed.
Execution halted