Error(s) in re-building vignettes:
--- re-building ‘traineR.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
Loading required package: rpart
Warning in strheight(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in strwidth(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in strwidth(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in strwidth(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in strwidth(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in strwidth(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in strwidth(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in strwidth(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in strwidth(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in strwidth(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in strwidth(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in strheight(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in strwidth(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in strwidth(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in strwidth(s[i], units[i], cex[i], font[i], vfont = NULL) :
  no font could be found for family "Arial"
Warning in min(combined.boxes$y1, na.rm = TRUE) :
  no non-missing arguments to min; returning Inf
Warning in max(combined.boxes$y2, na.rm = TRUE) :
  no non-missing arguments to max; returning -Inf
Quitting from lines 158-161 (traineR.Rmd) 
Error: processing vignette 'traineR.Rmd' failed with diagnostics:
replacement has length zero
--- failed re-building ‘traineR.Rmd’

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

Error: Vignette re-building failed.
Execution halted