barplot won't print unless executed in place

[sbellan61]

mydoc <- pptx()# title = "title" )
mydoc <- addSlide( mydoc, slide.layout = "Title and Content" )
## myPlot = qplot(Sepal.Length, Petal.Length, data = iris,  ## **works**
##   color = Species, size = Petal.Width, alpha = I(0.7) )
## mydoc = addPlot(mydoc, fun = function()  barplot(1:8, col = 1:8, fg='white', col.axis='white')) ## **works**
 myPlot = barplot(1:8) ## **doesn't work**
mydoc <- addPlot( doc = mydoc, fun = print, x = myPlot, 
  offx = 1, offy = 1, width = 6, height = 5 )
mydoc <- addFlexTable( doc = mydoc, FlexTable( head( iris ) ),
  offx = 8, offy = 2, width = 4.5, height = 3 )
filename <- "force_pos_size.pptx" # the document to produce
writeDoc( mydoc, file = filename )

Error in .jcall(slide, "I", "add", dml.object, width, height, offx, offy) : javax.xml.bind.UnmarshalException

• with linked exception: [org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 2; The markup in the document preceding the root element must be well-formed.]

[davidgohel]

You have this error because myPlot contains a vector not a ggplot object, print(myPlot) is not producing any plot.