Error(s) in re-building vignettes:
  ...
--- re-building ‘cars.Rmd’ using rmarkdown
[WARNING] This document format requires a nonempty <title> element.
  Defaulting to 'cars.knit' as the title.
  To specify a title, use 'title' in metadata or --metadata title="...".
--- finished re-building ‘cars.Rmd’

--- re-building ‘illusions.Rmd’ using rmarkdown
[WARNING] This document format requires a nonempty <title> element.
  Defaulting to 'illusions.knit' as the title.
  To specify a title, use 'title' in metadata or --metadata title="...".
--- finished re-building ‘illusions.Rmd’

--- re-building ‘maps.Rmd’ using rmarkdown
Quitting from lines 18-30 (maps.Rmd) 
Error: processing vignette ‘maps.Rmd’ failed with diagnostics:
The package `mapproj` is required for `coord_map()`
--- failed re-building ‘maps.Rmd’

--- re-building ‘math.Rmd’ using rmarkdown
[WARNING] Could not convert TeX math '\begin{aligned}
  \dot{x} &amp; = \sigma(y-x) \\
  \dot{y} &amp; = \rho x - y - xz \\
  \dot{z} &amp; = -\beta z + xy
  \end{aligned}', rendering as TeX
[WARNING] Could not convert TeX math ' P(E)   = {n \choose k} p^k (1-p)^{ n-k} ', rendering as TeX
[WARNING] Could not convert TeX math ' \frac{1}{\Bigl(\sqrt{\phi \sqrt{5}}-\phi\Bigr) e^{\frac25 \pi}} =
  1+\frac{e^{-2\pi}} {1+\frac{e^{-4\pi}} {1+\frac{e^{-6\pi}}
  {1+\frac{e^{-8\pi}} {1+\ldots} } } } ', rendering as TeX:
   \frac{1}{\Bigl(\sqrt{\phi \sqrt{5}}-\ph
                ^
  unexpected "("
  expecting "%", "\\label", "\\nonumber" or whitespace
[WARNING] This document format requires a nonempty <title> element.
  Defaulting to 'math.knit' as the title.
  To specify a title, use 'title' in metadata or --metadata title="...".
--- finished re-building ‘math.Rmd’

--- re-building ‘two-D.Rmd’ using rmarkdown
[WARNING] This document format requires a nonempty <title> element.
  Defaulting to 'two-D.knit' as the title.
  To specify a title, use 'title' in metadata or --metadata title="...".
--- finished re-building ‘two-D.Rmd’

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

Error: Vignette re-building failed.
Execution halted