How to remove dev.off() phrasing from the pdf output?

Question

I am creating a pdf file where I am "printing" a png with grid.draw() since it was a merge of two plots, therefore impossible to use ggsave since it was not a plot.

Anyways, when printing the result, everything is fine except the message from dev.off(). The console is as it follows:

# saving grid draw to a png (not a ggplot class, therefore other kind of saving is needed)
> png(filename = "data_x_plot.png",
+         pointsize = 500, 
+         width = 1200,
+         height = 1000,
+         units = "px") 
> grid.draw(data_x)
> dev.off()
RStudioGD 
        2 

And the code in the .Rnw script is as follows:

g1 <- ggplotGrob(p1)
g2 <- ggplotGrob(p2)
data_x <- rbind(g1, g2, size="first") # stack the two plots
data_x$widths <- unit.pmax(g1$widths, g2$widths) # use the largest widths

# saving grid draw to a png (not a ggplot class, therefore other kind of saving is needed)
png(filename = "data_x_plot.png",
    pointsize = 500, 
    width = 1200,
    height = 1000,
    units = "px") 
grid.draw(data_x)
dev.off()
@
  
  \begin{center}
\includegraphics[scale=0.37]{data_x_plot.png}
\captionof{figure}{Overview of the x data.}
\end{center}

Strangely, what is being printed to the pdf before each png.file is not "RStudioGD 2" , but "pdf 2" . I do not what "RStudioGD 2" to be printed out... I just want that this kind of messages do not pass to the pdf file.

Can you tell me how to avoid or how to hide this message from dev.off()?

Answer 1

As Rui Barradas, said in the comments, the solution is just replace the

dev.off()

by

invisible(capture.output(dev.off()))

Very easy solution to omit any message created by annoying functions.