Error(s) in re-building vignettes:
  ...
--- re-building ‘Custom_Steps.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
Error: processing vignette 'Custom_Steps.Rmd' failed with diagnostics:
there is no package called 'stringr'
--- failed re-building ‘Custom_Steps.Rmd’

--- re-building ‘Dummies.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
Error: processing vignette 'Dummies.Rmd' failed with diagnostics:
there is no package called 'stringr'
--- failed re-building ‘Dummies.Rmd’

--- re-building ‘Ordering.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
Error: processing vignette 'Ordering.Rmd' failed with diagnostics:
there is no package called 'stringr'
--- failed re-building ‘Ordering.Rmd’

--- re-building ‘Roles.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
Error: processing vignette 'Roles.Rmd' failed with diagnostics:
there is no package called 'stringr'
--- failed re-building ‘Roles.Rmd’

--- re-building ‘Selecting_Variables.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
Error: processing vignette 'Selecting_Variables.Rmd' failed with diagnostics:
there is no package called 'stringr'
--- failed re-building ‘Selecting_Variables.Rmd’

--- re-building ‘Simple_Example.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
Error: processing vignette 'Simple_Example.Rmd' failed with diagnostics:
there is no package called 'stringr'
--- failed re-building ‘Simple_Example.Rmd’

--- re-building ‘Skipping.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
Error: processing vignette 'Skipping.Rmd' failed with diagnostics:
there is no package called 'stringr'
--- failed re-building ‘Skipping.Rmd’

SUMMARY: processing the following files failed:
  ‘Custom_Steps.Rmd’ ‘Dummies.Rmd’ ‘Ordering.Rmd’ ‘Roles.Rmd’
  ‘Selecting_Variables.Rmd’ ‘Simple_Example.Rmd’ ‘Skipping.Rmd’

Error: Vignette re-building failed.
Execution halted