Unicode characters in plots to use in dynamic reports using R, Sweave and knitr

Question

I have a problem properly displaying fonts in plots generated by ggplot2 in LaTeX reports generated by R studio in Sweave using knitr.

At first I was not able to properly generate pdfs with polish fonts but that problem was tackled in this post:

Unicode Characters in ggplot2 PDF Output

In short, the author adviced using Cairo package (in R) to generate plots using ggplot2.

This worked for me - once -> meaning I was able to generate a plot with polish characters, but when I am trying to use it in sweave document to generate LaTeX report using knitr like this:

<<pieniadze_graph,fig=TRUE,echo=FALSE>>=
library(Cairo)
cairo_pdf("TutorialExercisesPart2-pieniadze_graph.pdf")  
plot1 <- qplot(expenditure, data = cas) + xlim(0, 8000) + 
    xlab(expression(paste("Pieniądze wydane na ucznia ($)"))) +
    ylab("Liczba szkółńćźżś")
print(plot1)
@ 

I get an error.:

Running pdflatex on TutorialExercisesPart2.tex...failed

While investigating while that happend -> i found that the file that cairo is soppoused to generate is blank (there is a pdf file of a name given to cairo_pdf but it can not be opened with pdf viewer -> error cannot open text file)

Now one note is necessary: The cairo_pdf function requires file name to be set. So I give the pdf a name, that is required to be used later by the tex file in a format filename-chunk_name.pdf (So much for dynamic reports :P)

So I am not for the cairo_pdf option. Is there a way to generate proper pdf files without cairo_pdf option?

I was not able to find anything more on this topic without the cairo-pdf...

When I delete the cairo part my tex file is generated nicely with an ugly looking dots labels PDF file in it...

Answer 1

Rather than opening a device like you do with calling cairo_pdf(), you should instruct knitr to use the device. Have a look at the knitr options and "dev" in particular. In summary, you need to

<<pieniadze_graph,fig=TRUE,echo=FALSE,dev='cairo_pdf'>>=
...

or to make it default for all chunks

opts_chunk$set(dev='cairo_pdf')

Answer 2

Ok I finally got it!

It really was a problem with Sweave coding in the chunk heading.

After @Matev's response I began testing the dev='cairo_pdf' -> but this did not change anything in the output.

Why? Because the

<<dev='cairo_pdf'>>=
@

is only interpreted by knitr Rnw file weaver!!! And I was using the Sweave weaver (this is set in the global options of R studio under Sweave section).

After recognising the not-so-obvious mistake (Because both Sweave and knitr use similar chunk heading script format) I seached what Leisch had to say about that in his Sweave Manual. This is his solution for everyone who has the same problem:

1. Put this code early in the document (after R libraries)

   <<>>=
   my.Swd <- function(name, width, height, ...)
   grDevices::cairo_pdf(filename = paste(name, "pdf", sep = "."),
   width = width, height = height)
   @
   

2. You may now use the following code in seperate chunks

   <<chunk_name,grdevice=my.Swd,fig=TRUE>>=
   @
   

or as @Matev adviced globally set chunk options for the entire document (but again his answer was for the knitr weaver):

    \SweaveOpts{grdevice=my.Swd}

Now You will get beautiful plots generated by the cairo_pdf device (base R device) which handles uniode fonts nicely!!! And they will get sweaved into Your dynamic reports like magic!

And I would like to thank Yihui for the knitr package which is GREAT!