I watched a great webinar by RStudio the other day about RMarkdown. After the webinar they posted the code used in the demonstrations online and I wanted to check out one example. I took [their code](https://raw.githubusercontent.com/rstudio/webinars/master/2014-01/4-linked-brush.Rmd), put it in my RStudio (which says it's fully up-to-date, v0.98.978), installed or updated all the necessary packages and hit "Run Document"

I receive an error which I do not understand and for which Google has been very unhelpful. What is this mysterious <document start> and how do I include it? I assumed all necessary components would be included given the source of the code.

```
Error in yaml::yaml.load(front_matter) : 
  Parser error: did not find expected <document start> at line 2, column 1
Calls: <Anonymous> -> parse_yaml_front_matter -> <Anonymous> -> .Call
Execution halted

```