Changing font in PDF produced by rmarkdown

Question

I am producing reports using rmarkdown. When knitting a PDF

---
title: "Untitled"
output: pdf_document
---

I would like to specify the font to be used in creating the PDF. The official documentation (see section "LaTeX Options) says I can do this. However, I've never used LaTeX and fail to understand how such selection can be made in YAML options at the top of the .Rmd document used by rmarkdown package.

Question: How do I change the font in the PDF produced by rmarkdown?

sessionInfo() R version 3.1.0 (2014-04-10) Platform: x86_64-w64-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United States.1252   
[3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] ggplot2_1.0.0 RODBC_1.3-10  knitr_1.6     dplyr_0.2

I've never used LaTeX and don't want to get into it at this very mom

Answer 1

The indentation in YAML options is meaningful. As the instructions point out "note that these options do not appear underneath the output section but rather appear at the top level along with title, author, etc.)". So,

---
output:
  pdf_document:
    latex_engine: xelatex
    sansfont: Calibri Light
---

will produce an unused argument error, while

---
output:
  pdf_document:
    latex_engine: xelatex
sansfont: Calibri Light
---

will do the job. In addition, LaTeX commands inserted after YAML seem to override it: so

---
output:
  pdf_document:
    latex_engine: xelatex
    sansfont: Calibri Light
---
\fontsize{12}{22}
\fontseries{b}
\selectfont

produces the PDF with default font, not Calibri, however, the font option is passed fine.