Error(s) in re-building vignettes:
--- re-building ‘RiemannBasic.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
** ------------------------------------------------------- **
**  Riemann || Learning with Data on Riemannian Manifolds      
**
** Version    : 0.1.3       (2021)
** Maintainer : Kisung You  (kisungyou@outlook.com)
** Website    : https://kisungyou.com/Riemann/
**
** Please share any bugs or suggestions to the maintainer.
** ------------------------------------------------------- **
Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
  Discarded datum unknown in Proj4 definition
Warning in grid.Call(C_stringMetric, as.graphicsAnnot(x$label)) :
  no font could be found for family "Arial"
Warning in grid.Call(C_stringMetric, as.graphicsAnnot(x$label)) :
  no font could be found for family "Arial"
Warning in grid.Call(C_stringMetric, as.graphicsAnnot(x$label)) :
  no font could be found for family "Arial"
Warning in grid.Call(C_stringMetric, as.graphicsAnnot(x$label)) :
  no font could be found for family "Arial"
Warning in grid.Call(C_stringMetric, as.graphicsAnnot(x$label)) :
  no font could be found for family "Arial"
Warning in grid.Call(C_stringMetric, as.graphicsAnnot(x$label)) :
  no font could be found for family "Arial"
Warning in grid.Call(C_stringMetric, as.graphicsAnnot(x$label)) :
  no font could be found for family "Arial"
Warning in grid.Call(C_stringMetric, as.graphicsAnnot(x$label)) :
  no font could be found for family "Arial"
Warning in grid.Call(C_stringMetric, as.graphicsAnnot(x$label)) :
  no font could be found for family "Arial"
Warning in grid.Call(C_stringMetric, as.graphicsAnnot(x$label)) :
  no font could be found for family "Arial"
Warning in grid.Call(C_stringMetric, as.graphicsAnnot(x$label)) :
  no font could be found for family "Arial"
Warning in grid.Call(C_stringMetric, as.graphicsAnnot(x$label)) :
  no font could be found for family "Arial"
Warning in grid.Call(C_stringMetric, as.graphicsAnnot(x$label)) :
  no font could be found for family "Arial"
Warning in grid.Call(C_stringMetric, as.graphicsAnnot(x$label)) :
  no font could be found for family "Arial"
Warning in grid.Call(C_textBounds, as.graphicsAnnot(x$label), x$x, x$y,  :
  no font could be found for family "Arial"
Quitting from lines 57-73 (RiemannBasic.Rmd) 
Error: processing vignette 'RiemannBasic.Rmd' failed with diagnostics:
polygon edge not found
--- failed re-building ‘RiemannBasic.Rmd’

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

Error: Vignette re-building failed.
Execution halted