This is something that nags me from time to time, particularly because it’s a documented feature I tend to forget. When using the split.screen() function of R to combine plots (rather than par(mfrow)) in Sweave or Knitr, the screen numbers are output in the main text, alongside the figure. Usually we want the figure only. All we need is adding results='hide'. I find this slightly counter-intuitive, because I do want the result (in form of a figure). That said, I don’t have a suggestion what alternative would feel more intuitive. The same issue also happens when using library(rgdal) for a local shapefile, and other similar situations.
Published 29 March 2016