This vignette shows some examples for different Markdown extensions and HTML options.

    library(markdown)

# Markdown Extensions

    # The following examples are short, so we set the HTML option 'fragment_only'

    options(markdown.HTML.options = "fragment_only")

    # no_intra_emphasis example
    cat(markdownToHTML(text = "foo_bar_function", extensions = c()))

    ## <p>foo<em>bar</em>function</p>

    cat(markdownToHTML(text = "foo_bar_function", extensions = c("no_intra_emphasis")))

    ## <p>foo_bar_function</p>

    # tables example (need 4 spaces at beginning of line here)
    cat(markdownToHTML(text = "
        First Header  | Second Header
        ------------- | -------------
        Content Cell  | Content Cell
        Content Cell  | Content Cell
    ", extensions = c()))

    ## <pre><code>First Header  | Second Header
    ## ------------- | -------------
    ## Content Cell  | Content Cell
    ## Content Cell  | Content Cell
    ## </code></pre>

    # but not here
    cat(markdownToHTML(text = "
    First Header  | Second Header
    ------------- | -------------
    Content Cell  | Content Cell
    Content Cell  | Content Cell
    ", extensions = c("tables")))

    ## <table><thead>
    ## <tr>
    ## <th>First Header</th>
    ## <th>Second Header</th>
    ## </tr>
    ## </thead><tbody>
    ## <tr>
    ## <td>Content Cell</td>
    ## <td>Content Cell</td>
    ## </tr>
    ## <tr>
    ## <td>Content Cell</td>
    ## <td>Content Cell</td>
    ## </tr>
    ## </tbody></table>

    # fenced_code example (need at least three leading ~ or `)
    fenced_block <- function(text, x = "`", n = 3) {
      fence <- paste(rep(x, n), collapse = "")
      paste(fence, text, fence, sep = "")
    }
    cat(markdownToHTML(text = fenced_block("
    preformatted text here without having to indent
    first line.
    "), extensions = c()))

    ## <p><code>
    ## preformatted text here without having to indent
    ## first line.
    ## </code></p>

    cat(markdownToHTML(text = fenced_block("
    preformatted text here without having to indent
    first line.
    "), extensions = c("fenced_code")))

    ## <pre><code>preformatted text here without having to indent
    ## first line.
    ## </code></pre>

    # autolink example
    cat(markdownToHTML(text = "https://www.r-project.org/", extensions = c()))

    ## <p>https://www.r-project.org/</p>

    cat(markdownToHTML(text = "https://www.r-project.org/", extensions = c("autolink")))

    ## <p><a href="https://www.r-project.org/">https://www.r-project.org/</a></p>

    # strikethrough example
    cat(markdownToHTML(text = "~~awesome~~", extensions = c()))

    ## <p>~~awesome~~</p>

    cat(markdownToHTML(text = "~~awesome~~", extensions = c("strikethrough")))

    ## <p><del>awesome</del></p>

    # lax_spacing
    cat(markdownToHTML(text = "
    Embedding html without surrounding with empty newline.
    <div>_markdown_</div>
    extra text.
    ", extensions = c("")))

    ## <p>Embedding html without surrounding with empty newline.
    ## <div><em>markdown</em></div>
    ## extra text.</p>

    cat(markdownToHTML(text = "
    Embedding html without surrounding with empty newline.
    <div>_markdown_</div>
    extra text.
    ", extensions = c("lax_spacing")))

    ## <p>Embedding html without surrounding with empty newline.</p>
    ##
    ## <div>_markdown_</div>
    ##
    ## <p>extra text.</p>

    # space_headers example
    cat(markdownToHTML(text = "#A Header\neven though there is no space between # and A",
                       extensions = c("")))

    ## <h1>A Header</h1>
    ##
    ## <p>even though there is no space between # and A</p>

    cat(markdownToHTML(text = "#Not A Header\nbecause there is no space between # and N",
                       extensions = c("space_headers")))

    ## <p>#Not A Header
    ## because there is no space between # and N</p>

    # superscript example
    cat(markdownToHTML(text = "2^10", extensions = c()))

    ## <p>2^10</p>

    cat(markdownToHTML(text = "2^10", extensions = c("superscript")))

    ## <p>2<sup>10</sup></p>

# HTML Options

    # HTML OPTIONS

    # The following examples are short, so we allways add the HTML option 'fragment_only'
    tOpt <- "fragment_only"

    # skip_html example
    mkd = '<style></style><img src="file:///usr/lib/R/site-library/markdown/html/Rlogo.jpg"><a href="#">Hello</a>'
    cat(markdownToHTML(text = mkd, options = c(tOpt)))

    ## <p><style></style><img src="file:///usr/lib/R/site-library/markdown/html/Rlogo.jpg"><a href="#">Hello</a></p>

    cat(markdownToHTML(text = mkd, options = c(tOpt, "skip_html")))

    ## <p>Hello</p>

    # skip_style example
    cat(markdownToHTML(text = mkd, options = c(tOpt)))

    ## <p><style></style><img src="file:///usr/lib/R/site-library/markdown/html/Rlogo.jpg"><a href="#">Hello</a></p>

    cat(markdownToHTML(text = mkd, options = c(tOpt, "skip_style")))

    ## <p><img src="file:///usr/lib/R/site-library/markdown/html/Rlogo.jpg"><a href="#">Hello</a></p>

    # skip_images example
    cat(markdownToHTML(text = mkd, options = c(tOpt)))

    ## <p><style></style><img src="file:///usr/lib/R/site-library/markdown/html/Rlogo.jpg"><a href="#">Hello</a></p>

    cat(markdownToHTML(text = mkd, options = c(tOpt, "skip_images")))

    ## <p><style></style><a href="#">Hello</a></p>

    # skip_links example
    cat(markdownToHTML(text = mkd, options = c(tOpt)))

    ## <p><style></style><img src="file:///usr/lib/R/site-library/markdown/html/Rlogo.jpg"><a href="#">Hello</a></p>

    cat(markdownToHTML(text = mkd, options = c(tOpt, "skip_links")))

    ## <p><style></style><img src="file:///usr/lib/R/site-library/markdown/html/Rlogo.jpg">Hello</p>

    # safelink example
    cat(markdownToHTML(text = '[foo](http://google.com "baz")', options = c(tOpt)))

    ## <p><a href="http://google.com" title="baz">foo</a></p>

    cat(markdownToHTML(text = '[foo](http://google.com "baz")', options = c(tOpt, "safelink")))

    ## <p><a href="http://google.com" title="baz">foo</a></p>

    # toc example
    mkd <- paste(c("# Header 1", "p1", "## Header 2", "p2"), collapse = "\n")

    cat(markdownToHTML(text = mkd, options = c(tOpt)))

    ## <h1>Header 1</h1>
    ##
    ## <p>p1</p>
    ##
    ## <h2>Header 2</h2>
    ##
    ## <p>p2</p>

    cat(markdownToHTML(text = mkd, options = c(tOpt, "toc")))

    ## <div id="toc">
    ## <div id="toc_header">Table of Contents</div>
    ## <ul>
    ## <li>
    ## <a href="#toc_0">Header 1</a>
    ## <ul>
    ## <li>
    ## <a href="#toc_1">Header 2</a>
    ## </li>
    ## </ul>
    ## </li>
    ## </ul>
    ## </div>
    ##
    ##
    ## <h1 id="toc_0">Header 1</h1>
    ##
    ## <p>p1</p>
    ##
    ## <h2 id="toc_1">Header 2</h2>
    ##
    ## <p>p2</p>

    # hard_wrap example
    cat(markdownToHTML(text = "foo\nbar\n", options = c(tOpt)))

    ## <p>foo
    ## bar</p>

    cat(markdownToHTML(text = "foo\nbar\n", options = c(tOpt, "hard_wrap")))

    ## <p>foo<br>
    ## bar</p>

    # use_xhtml example
    cat(markdownToHTML(text = "foo\nbar\n", options = c(tOpt, "hard_wrap")))

    ## <p>foo<br>
    ## bar</p>

    cat(markdownToHTML(text = "foo\nbar\n", options = c(tOpt, "hard_wrap", "use_xhtml")))

    ## <p>foo<br/>
    ## bar</p>

    # escape example
    mkd = '<style></style><img src="file:///usr/lib/R/site-library/markdown/html/Rlogo.jpg"><a href="#">Hello</a>'
    cat(markdownToHTML(text = mkd, options = c(tOpt, "skip_html")))

    ## <p>Hello</p>

    # overrides all 'skip_*' options
    cat(markdownToHTML(text = mkd, options = c(tOpt, "skip_html", "escape")))

    ## <p>&lt;style&gt;&lt;/style&gt;&lt;img src=&quot;file:///usr/lib/R/site-library/markdown/html/Rlogo.jpg&quot;&gt;&lt;a href=&quot;#&quot;&gt;Hello&lt;/a&gt;</p>

    # smartypants example
    cat(markdownToHTML(text = "1/2 (c)", options = c(tOpt)))

    ## <p>1/2 (c)</p>

    cat(markdownToHTML(text = "1/2 (c)", options = c(tOpt, "smartypants")))

    ## <p>&frac12; &copy;</p>

    cat(smartypants(text = "1/2 (c)\n"))

    ## &frac12; &copy;