Error(s) in re-building vignettes:
  ...
--- re-building ‘bias-structures.Rmd’ using rmarkdown
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

Warning in if (class(x) == "unit") { :
  the condition has length > 1 and only the first element will be used
Warning in if (class(x) == "unit") { :
  the condition has length > 1 and only the first element will be used
Warning in if (class(x) == "unit") { :
  the condition has length > 1 and only the first element will be used
Warning in if (class(x) == "unit") { :
  the condition has length > 1 and only the first element will be used
Quitting from lines 37-40 (bias-structures.Rmd) 
Error: processing vignette 'bias-structures.Rmd' failed with diagnostics:
VECTOR_ELT() can only be applied to a 'list', not a 'double'
--- failed re-building ‘bias-structures.Rmd’

--- re-building ‘intro-to-dags.Rmd’ using rmarkdown
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 33-36 (intro-to-dags.Rmd) 
Error: processing vignette 'intro-to-dags.Rmd' failed with diagnostics:
VECTOR_ELT() can only be applied to a 'list', not a 'double'
--- failed re-building ‘intro-to-dags.Rmd’

--- re-building ‘intro-to-ggdag.Rmd’ using rmarkdown
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 59-60 (intro-to-ggdag.Rmd) 
Error: processing vignette 'intro-to-ggdag.Rmd' failed with diagnostics:
VECTOR_ELT() can only be applied to a 'list', not a 'double'
--- 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