dyEvent Example for https://github.com/rstudio/dygraphs/issues/122

example.Rmd

---
title: "dyEvent Example"
output:
  html_document:
    css: style.css
---

```{r setup, echo = FALSE, warning = FALSE, message = FALSE}
library(xts)
library(dygraphs)
knitr::opts_chunk$set(echo = FALSE)
```

```{r data}
example <- xts(data.frame(data = cumsum(rnorm(90))), order.by = seq(Sys.Date() - 90, Sys.Date() - 1, "day"))
```

```{r dygraph}
dygraph(example, main = "Random Walk") %>%
  dyCSS("style.css") %>%
  dyEvent(Sys.Date() - 7, "Last week", color = "white")
```

style.css

body {
  color: white;
  background-color: black;
}
.dygraph-title {
  color: white;
  font-weight: bold;
}
.dygraph-axis-label {
  color: white;
}
.dygraph-legend {
  color: black;
}