Error(s) in re-building vignettes:
  ...
--- re-building ‘bias-structures.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
Loading required package: ggplot2

Attaching package: 'ggdag'

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

    expand_scale

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

    filter

Quitting from lines 123-124 (bias-structures.Rmd) 
Error: processing vignette 'bias-structures.Rmd' failed with diagnostics:
replacement has length zero
--- failed re-building ‘bias-structures.Rmd’

--- re-building ‘intro-to-dags.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
Loading required package: ggplot2

Attaching package: 'ggdag'

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

    expand_scale

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

    filter

Quitting from lines 41-43 (intro-to-dags.Rmd) 
Error: processing vignette 'intro-to-dags.Rmd' failed with diagnostics:
invalid argument to unary operator
--- failed re-building ‘intro-to-dags.Rmd’

--- re-building ‘intro-to-ggdag.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
Loading required package: ggplot2

Attaching package: 'ggdag'

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

    expand_scale

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

    filter


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 147-155 (intro-to-ggdag.Rmd) 
Error: processing vignette 'intro-to-ggdag.Rmd' failed with diagnostics:
invalid argument to unary operator
--- failed re-building ‘intro-to-ggdag.Rmd’

SUMMARY: processing the following files failed:
  ‘bias-structures.Rmd’ ‘intro-to-dags.Rmd’ ‘intro-to-ggdag.Rmd’

Error: Vignette re-building failed.
Execution halted