Running examples in ‘cowplot-Ex.R’ failed
The error most likely occurred in:

> ### Name: stamp
> ### Title: Stamp plots with a label, such as good, bad, or ugly.
> ### Aliases: stamp stamp_good stamp_bad stamp_wrong stamp_ugly
> 
> ### ** Examples
> 
> library(ggplot2)
> 
> p <- ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width)) +
+   geom_point(aes(color = factor(Petal.Width)))
> 
> stamp_bad(p + guides(color = "none"))
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_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"
> stamp_ugly(p)
Warning in grid.Call(C_textBounds, as.graphicsAnnot(x$label), x$x, x$y,  :
  no font could be found for family "Arial"
Warning in grid.Call(C_textBounds, as.graphicsAnnot(x$label), x$x, x$y,  :
  no font could be found for family "Arial"
Error in grid.Call(C_textBounds, as.graphicsAnnot(x$label), x$x, x$y,  : 
  polygon edge not found
Calls: stamp_ugly ... <Anonymous> -> widthDetails -> widthDetails.text -> grid.Call
Execution halted