Error(s) in re-building vignettes:
--- re-building ‘Generating_syntax.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
This is lavaan 0.6-9
lavaan is FREE software! Please report any bugs.

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

--- finished re-building ‘Generating_syntax.Rmd’

--- re-building ‘Plotting_graphs.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
This is lavaan 0.6-9
lavaan is FREE software! Please report any bugs.

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 286-289 (Plotting_graphs.Rmd) 
Error: processing vignette 'Plotting_graphs.Rmd' failed with diagnostics:
polygon edge not found
--- failed re-building ‘Plotting_graphs.Rmd’

--- re-building ‘Tabulating_results.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
--- finished re-building ‘Tabulating_results.Rmd’

--- re-building ‘sem_graph.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
Warning in lav_object_post_check(object) :
  lavaan WARNING: some estimated ov variances are negative
Warning in lav_partable_check(lavpartable, categorical = lavoptions$categorical,  :
  lavaan WARNING: parameter table does not contain intercepts for one or more variables: [y_1 y_2 y_3]
Warning in lav_object_post_check(object) :
  lavaan WARNING: some estimated ov variances are negative
Warning in lav_object_post_check(object) :
  lavaan WARNING: some estimated ov variances are negative
--- finished re-building ‘sem_graph.Rmd’

SUMMARY: processing the following file failed:
  ‘Plotting_graphs.Rmd’

Error: Vignette re-building failed.
Execution halted