Error(s) in re-building vignettes:
  ...
--- re-building 'introduction.Rmd' using rmarkdown
--- finished re-building 'introduction.Rmd'

--- re-building 'recreating_analyses.Rmd' using rmarkdown
Joining, by = "Month"
Quitting from lines 348-367 (recreating_analyses.Rmd) 
Error: processing vignette 'recreating_analyses.Rmd' failed with diagnostics:
Can't convert NULL to a symbol.
--- failed re-building 'recreating_analyses.Rmd'

SUMMARY: processing the following file failed:
  'recreating_analyses.Rmd'

Error: Vignette re-building failed.
Execution halted
Error(s) in re-building vignettes:
  ...
--- re-building ‘introduction.Rmd’ using rmarkdown
--- finished re-building ‘introduction.Rmd’

--- re-building ‘recreating_analyses.Rmd’ using rmarkdown
Joining, by = "Month"
Quitting from lines 348-367 (recreating_analyses.Rmd) 
Error: processing vignette ‘recreating_analyses.Rmd’ failed with diagnostics:
Can't convert NULL to a symbol.
--- failed re-building ‘recreating_analyses.Rmd’

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

Error: Vignette re-building failed.
Execution halted
Error(s) in re-building vignettes:
--- re-building ‘introduction.Rmd’ using rmarkdown
--- finished re-building ‘introduction.Rmd’

--- re-building ‘recreating_analyses.Rmd’ using rmarkdown
Joining, by = "Month"
Quitting from lines 348-367 (recreating_analyses.Rmd) 
Error: processing vignette 'recreating_analyses.Rmd' failed with diagnostics:
Can't convert NULL to a symbol.
--- failed re-building ‘recreating_analyses.Rmd’

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

Error: Vignette re-building failed.
Execution halted
Error(s) in re-building vignettes:
--- re-building ‘introduction.Rmd’ using rmarkdown
--- finished re-building ‘introduction.Rmd’

--- re-building ‘recreating_analyses.Rmd’ using rmarkdown
Joining, by = "Month"
Quitting from lines 348-367 (recreating_analyses.Rmd) 
Error: processing vignette 'recreating_analyses.Rmd' failed with diagnostics:
Can't convert NULL to a symbol.
--- failed re-building ‘recreating_analyses.Rmd’

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

Error: Vignette re-building failed.
Execution halted
Error(s) in re-building vignettes:
--- re-building 'introduction.Rmd' using rmarkdown
--- finished re-building 'introduction.Rmd'

--- re-building 'recreating_analyses.Rmd' using rmarkdown
Joining, by = "Month"
Quitting from lines 348-367 (recreating_analyses.Rmd) 
Error: processing vignette 'recreating_analyses.Rmd' failed with diagnostics:
Can't convert NULL to a symbol.
--- failed re-building 'recreating_analyses.Rmd'

SUMMARY: processing the following file failed:
  'recreating_analyses.Rmd'

Error: Vignette re-building failed.
Execution halted
Error(s) in re-building vignettes:
--- re-building 'introduction.Rmd' using rmarkdown
--- finished re-building 'introduction.Rmd'

--- re-building 'recreating_analyses.Rmd' using rmarkdown
Joining, by = "Month"
Quitting from lines 348-367 (recreating_analyses.Rmd) 
Error: processing vignette 'recreating_analyses.Rmd' failed with diagnostics:
Can't convert NULL to a symbol.
--- failed re-building 'recreating_analyses.Rmd'

SUMMARY: processing the following file failed:
  'recreating_analyses.Rmd'

Error: Vignette re-building failed.
Execution halted
Error(s) in re-building vignettes:
  ...
--- re-building ‘introduction.Rmd’ using rmarkdown
--- finished re-building ‘introduction.Rmd’

--- re-building ‘recreating_analyses.Rmd’ using rmarkdown
Joining, by = "Month"
Quitting from lines 348-367 (recreating_analyses.Rmd) 
Error: processing vignette 'recreating_analyses.Rmd' failed with diagnostics:
Can't convert NULL to a symbol.
--- failed re-building ‘recreating_analyses.Rmd’

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

Error: Vignette re-building failed.
Execution halted
Error(s) in re-building vignettes:
  ...
--- re-building ‘introduction.Rmd’ using rmarkdown
--- finished re-building ‘introduction.Rmd’

--- re-building ‘recreating_analyses.Rmd’ using rmarkdown
Joining, by = "Month"
Quitting from lines 348-367 (recreating_analyses.Rmd) 
Error: processing vignette 'recreating_analyses.Rmd' failed with diagnostics:
Can't convert NULL to a symbol.
--- failed re-building ‘recreating_analyses.Rmd’

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

Error: Vignette re-building failed.
Execution halted
Error(s) in re-building vignettes:
--- re-building 'introduction.Rmd' using rmarkdown
--- finished re-building 'introduction.Rmd'

--- re-building 'recreating_analyses.Rmd' using rmarkdown
Joining, by = "Month"
Quitting from lines 348-367 (recreating_analyses.Rmd) 
Error: processing vignette 'recreating_analyses.Rmd' failed with diagnostics:
Can't convert NULL to a symbol.
--- failed re-building 'recreating_analyses.Rmd'

SUMMARY: processing the following file failed:
  'recreating_analyses.Rmd'

Error: Vignette re-building failed.
Execution halted
Error(s) in re-building vignettes:
--- re-building 'introduction.Rmd' using rmarkdown
--- finished re-building 'introduction.Rmd'

--- re-building 'recreating_analyses.Rmd' using rmarkdown
Joining, by = "Month"
Quitting from lines 348-367 (recreating_analyses.Rmd) 
Error: processing vignette 'recreating_analyses.Rmd' failed with diagnostics:
Can't convert NULL to a symbol.
--- failed re-building 'recreating_analyses.Rmd'

SUMMARY: processing the following file failed:
  'recreating_analyses.Rmd'

Error: Vignette re-building failed.
Execution halted