Many R users (especially on Linux)
produce documents and reports using LaTeX for typesetting
and PDF or PostScript as the final output format.
If the document includes a plot produced by R, it can be
useful to use the same font in the plot as is used in the
main text of the document. The default font in LaTeX
is Donald Knuth's Computer Modern, so the issue is
how to use Computer Modern fonts in R (PDF and PostScript) graphics.
R allows the user to specify special fonts for graphics (see "Fonts, Lines, and Transparency" in volume 4(2) of http://cran.r-project.org/doc/Rnews), but the Computer Modern fonts are special in a couple of ways:
For example, character 60 [character 074 in octal, 0x3C in hex] for the "plain" text Computer Modern font is an upside down exclamation mark, instead of the more typical ASCII less-than sign [<])
Worse, many of the different Computer Modern fonts have their own special encoding: for the typewriter font, character 60 is the usual less-than sign; for math symbol font, character 60 is the R-fractur character.
Special encodings are not necessarily a problem, because it is possible to tell R about the encoding for a font. What is a problem, is that for the symbol face in R graphics text (face 5), R assumes that the symbol font uses the Adobe Symbol encoding. If you supply a font for the symbol face which is not in Adobe Symbol encoding, the wrong characters will be drawn.
For example, the plain text fonts do not contain a less-than sign, and the math symbol font does not contain an equals sign!
This means that, in order to draw text using a very standard, unexotic set of characters, you have to use a combination of more than one font.
In R graphics, it is only possible to specify a single font, and in fact only a single font face, for drawing a piece of text. This restriction is lifted somewhat when drawing mathematical annotations (see ?plotmath), where it is possible to use different font faces, and the symbol face is automatically employed to draw special mathematical symbols. But this is still not enough; even to draw quite normal text using a Computer Modern font, you need more than one font.
The real killer is that, because the symbol face is assumed to be in Adobe Symbol encoding, the font provided for the symbol face must include all of the characters defined in the Adobe Symbol encoding. And yes, the Adobe Symbol encoding includes both a less-than sign and an equals sign (among many others).
The solution for producing plain text is actually quite straightforward. All of the comments in the previous section about the peculiarity of the Computer Modern fonts were largely "straw man" comments (i.e., totally unfair). They are true of the Type 1 Computer Modern fonts that are distributed as part of a standard LaTeX set up (i.e., Computer Modern fonts designed for use with LaTeX which of course has no problem with TeX-specific encodings and character sets), but those are not the only Type 1 Computer Modern fonts around.
The TeX package cm-lgc contains Type 1 Computer Modern fonts which are set up for use with non-TeX encoding schemes; they contain more complete character sets. All we need to do is download (and possibly install) these fonts then we can produce normal text in R PostScript and PDF graphics output (see the examples below).
Another set of Computer Modern fonts with non-TeX encodings is provided by the cm-super package. Andrey Paramonov reports that this solves a problem with cm-lgc where Cyrillic encodings lack the "minus" character (thanks Andrey!).
The solution for producing mathematical annotation is harder, but
is mostly solved. This has required creating a new, customised
Computer Modern font containing appropriate Adobe Symbol characters
in the Adobe Symbol encoding. You can read about
the gory details if you like, but the
important part is that you can download an AFM
file and a PFB file for use as the
symbol face in a Computer Modern family of fonts for producing
mathematical annotation in PostScript and PDF graphics output
Suppose that cm-lgc has been downloaded and unzipped in
the current directory (creates a directory called cm-lgc
containing various other directories and files).
Suppose also, that the AFM and PFB files for the new cmsyase font
are in the current working directory.
The following code produces the mathematical annotation demo
using Computer Modern fonts (updated 2010-06-11; tested on R 2.12.0).
CM <- Type1Font("CM", c("cm-lgc/fonts/afm/public/cm-lgc/fcmr8a.afm", "cm-lgc/fonts/afm/public/cm-lgc/fcmb8a.afm", "cm-lgc/fonts/afm/public/cm-lgc/fcmri8a.afm", "cm-lgc/fonts/afm/public/cm-lgc/fcmbi8a.afm", "./cmsyase.afm")) pdf("destructiontest.pdf", family=CM) demo(plotmath) dev.off() embedFonts("destructiontest.pdf", fontpaths=c("cm-lgc/fonts/type1/public/cm-lgc/", "."))A complete test of the new cmsyase font is produced by this R code. The output using the standard Adobe Helvetica and Symbol fonts looks like this and the output using the cm-lgc and cmsyase fonts looks like this.
One way to view a file produced by R that contains a special font
is to use
ghostscript and just tell it where the font files are.
For example ...
GS_FONTPATH=cm-lgc/fonts/type1/public/cm-lgc:. gs -sDEVICE=x11 yourfile.pdfFor printing (or inclusion in other documents), ghostscript can be used to do the embedding. For example ...
GS_FONTPATH=cm-lgc/fonts/type1/public/cm-lgc:. gs -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=yourfileembed.pdf yourfile.pdfThis creates a file that has the fonts embedded, so you can send it to a printer or to a friend and the printer or friend's viewer software will be able to find the fonts in the file.
R now has an
embedFonts() function that will do this
font embedding (via ghostscript) from within an R session.
For inclusion of R graphics files in LaTeX documents,
especially when working with a large report or a book
(where embedding the fonts in each
graphic file is inefficient; it is better to embed the fonts in the
overall file), I had suspected that
pdflatex could do the font embedding,
and Daniel Sabanes Bove has subsequently
provided a description of how to do this (I have not tried this out
myself yet, but intend to soon; thanks Daniel!):
We are almost done, only the mapping file needs some changes: The files
have to be named relative to
the compilation directory. Adding the prefixes
After configuring the correct paths in the font description in the Rnw-file myfile.Rnw, we can run R with Sweave and process the dvi-file with the command
dvips -Ppdf -u +fonts/cm-lgc.map myfile.dviFinally, we can assure that ps2pdf embeds the necessary fonts by executing
ps2pdf14 -dSubsetFonts=true -dEmbedAllFonts=true myfile.ps