R markdown link is not formatted blue when knitted to pdf

Question

for some reason no link in my R markdowns (rmd) is formatted blue. knitting the simple rmd below to pdf is leaving the text color black. only when hovering over it does one realize that it's actually a link. knitting it to html will make the link blue. of course I can use a latex wrapper but I wonder why that is?

sessionInfo() R version 3.3.0 (2016-05-03) Platform: x86_64-w64-mingw32/x64 (64-bit) Running under: Windows 7 x64 (build 7601) Service Pack 1 loaded via a namespace (and not attached): knitr_1.15

RStudio 1.0.44

---
title: "R Notebook"
output:
  pdf_document: default
  html_notebook: default
---

```{r, echo=F}
# tex / pandoc options for pdf creation
x <- Sys.getenv("PATH")
y <- paste(x, "E:\\miktex\\miktex\\bin", sep=";")
Sys.setenv(PATH = y)
```

[link](www.rstudio.com)

Answer 1

Add urlcolor: blue to the yaml.

---
title: "R Notebook"
output:
  pdf_document: default
  html_notebook: default
urlcolor: blue
---

```{r, echo=F}
# tex / pandoc options for pdf creation
x <- Sys.getenv("PATH")
y <- paste(x, "E:\\miktex\\miktex\\bin", sep=";")
Sys.setenv(PATH = y)
```

[Link to R Studio](www.rstudio.com)

Bare urls will also be highlighted:

http://www.rstudio.com

Answer 2

To elaborate on the answer by @eipi10, and to answer a question in the comments by @Maarten Punt, the urlcolor is specifying the color for URL links referenced in the doc. However you might have links to other sections in your document, specified by linkcolor . So you can specify either:

---
title: "R Notebook"
output:
  pdf_document: default
urlcolor: blue
linkcolor: red
---

## test links vs urls

* see [the relevant section](#test)



[link](http://www.rstudio.com)


```{r cars}
summary(cars)
```

\newpage

## Including Plots{#test}

You can also embed plots, for example:

```{r pressure, echo=FALSE}
plot(pressure)
```

The red is a link within the document, whereas the blue is a URL link.