It appears there is an easier way now by adding two arguments to the r chunk:
out.width= "65%", out.extra='style="float:right; padding:10px"'
This scales the plot to 65% of the page width and lets text float on the left side with a distance of 10px.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…