This is an example of Markdown vignettes in R. Before R 3.0.0, only Sweave/PDF vignettes were supported in R. Markdown is gaining popularity over the years due to its simplicity, and R 3.0.0 starts to support package vignettes written in R Markdown.

> Please note this example is for R Markdown v1 only. If you use R Markdown v2, you should use the vignette engine `knitr::rmarkdown` instead of `knitr::knitr`.

## Package vignettes

To enable Markdown vignettes in an R package, you need to

- add `*.Rmd` files under the `vignettes` directory
- add `VignetteBuilder: knitr` to the `DESCRIPTION` file
- specify the vignette engine `\VignetteEngine{knitr::knitr}` in the `Rmd` files (inside HTML comments)

## View vignettes

And R will load the knitr package to build these vignettes to HTML files, and you can see them when you open the HTML help:

    help(package = "YourPackage", help_type = "html")
    # or see a standalone list of vignettes
    browseVignettes("YourPackage")

## Examples

Below are some code chunks as examples.

    if (TRUE) cat("_hello_ **markdown**!", "\n")

hello markdown!

Normally you do not need any chunk options.

    1 + 1
    ## [1] 2
    10:1
    ##  [1] 10  9  8  7  6  5  4  3  2  1
    rnorm(5)^2
    ## [1] 1.554860 0.678517 3.577054 0.005221 0.886564
    strsplit("hello, markdown vignettes", "")
    ## [[1]]
    ##  [1] "h" "e" "l" "l" "o" "," " " "m" "a" "r" "k" "d" "o" "w" "n" " " "v"
    ## [18] "i" "g" "n" "e" "t" "t" "e" "s"

Feel free to draw beautiful plots and write math \(P(X>x)=\alpha/2\).

    n = 300
    set.seed(123)
    par(mar = c(4, 4, 0.1, 0.1))
    plot(rnorm(n), rnorm(n), pch = 21, cex = 5 * runif(n), col = "white", bg = "gray")

You can use your own CSS file instead of the built-in style in the markdown package – just set the option `markdown.HTML.stylesheet`, e.g.

    options(markdown.HTML.stylesheet = "path/to/a/custom/style.css")