Error(s) in re-building vignettes:
  ...
--- re-building ‘RWsearch-1-Introduction.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 'RWsearch-1-Introduction.Rmd' failed with diagnostics:
there is no package called 'stringr'
--- failed re-building ‘RWsearch-1-Introduction.Rmd’

--- re-building ‘RWsearch-2-Display-Download-Documentation.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 'RWsearch-2-Display-Download-Documentation.Rmd' failed with diagnostics:
there is no package called 'stringr'
--- failed re-building ‘RWsearch-2-Display-Download-Documentation.Rmd’

--- re-building ‘RWsearch-3-Package-versions-and-dependencies.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 'RWsearch-3-Package-versions-and-dependencies.Rmd' failed with diagnostics:
there is no package called 'stringr'
--- failed re-building ‘RWsearch-3-Package-versions-and-dependencies.Rmd’

--- re-building ‘RWsearch-4-Tools-for-taskviews.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 'RWsearch-4-Tools-for-taskviews.Rmd' failed with diagnostics:
there is no package called 'stringr'
--- failed re-building ‘RWsearch-4-Tools-for-taskviews.Rmd’

--- re-building ‘RWsearch-5-Web-search-engines.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 'RWsearch-5-Web-search-engines.Rmd' failed with diagnostics:
there is no package called 'stringr'
--- failed re-building ‘RWsearch-5-Web-search-engines.Rmd’

SUMMARY: processing the following files failed:
  ‘RWsearch-1-Introduction.Rmd’
  ‘RWsearch-2-Display-Download-Documentation.Rmd’
  ‘RWsearch-3-Package-versions-and-dependencies.Rmd’
  ‘RWsearch-4-Tools-for-taskviews.Rmd’
  ‘RWsearch-5-Web-search-engines.Rmd’

Error: Vignette re-building failed.
Execution halted