1

I'm working with the R package slidify to create revealjs slides. I'd like to reveal code fragments incrementally using the RMarkdown (rather than edit the resulting HTML) but can't seem to figure out a way.

In the example below I have two code chunks and I'd like the second to occur only after the preceding paragraph. I can go in to the resulting HTML and add class=fragment to the pre tag, but this is very inefficient!

Suggestions

---
title       : RevealJS with Bootstrap
framework   : revealjs
---

```{r}
mean(1:3)
```

<div class="fragment">
This works fine, the div does not appear until you click forward in the deck. But you can't put the div tags around a code fragment.
</div>


```{r}
mean(1:3)
```
ZRoss
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1 Answers1

1

You might have already answered for yourself by now, but one solution would be using knitr hooks. Here is a simple example:

---
title       : RevealJS with Bootstrap
framework   : revealjs
---

```{r cache=F,echo=F}
s0 <- knitr::knit_hooks$get('source')
o0 <- knitr::knit_hooks$get('output')

knitr::knit_hooks$set(
  list(
    source=function(x,options){
      if (is.null(options$class)) s0(x, options)
      else
        paste0(
          paste0("<div class='", options$class, "'><pre><code>")
          ,x
          ,'</code></pre>\n'
        )
    }
    ,output = function(x,options){
      if (is.null(options$class)) o0(x, options)
      else 
        paste0(
          "<pre><code>"
          ,x
          ,'</code></pre></div>\n'
        )
    }
  )
)
```

```{r class="fragment"}
mean(1:3)
```

<div class="fragment">
  This works fine, the div does not appear until you click forward in the deck. But you can't put the div tags around a code fragment.
</div>


```{r class="fragment"}
mean(1:3)
```
timelyportfolio
  • 6,479
  • 30
  • 33
  • This is very close so I marked as an answer. But the one issue with this is that it doesn't work with collapse=TRUE which is important to my slides. I added a gist that fixes this issue but it doesn't work with code chunks that have plots. https://gist.github.com/zross/6fe6c9d494646245a864 – ZRoss Oct 17 '14 at 19:20
  • I can't answer the whole question, but I modified @timelyportfolio's answer to work with plots (I didn't need to show code in my presentations) https://gist.github.com/srvanderplas/68d73ee4c6fdead4ed32 – srvanderplas Mar 24 '15 at 17:58