caption in the html output of knitr

Question

When knitting the following Rmd file

```{r, fig.cap="mycaption"}
plot(0,0,axes=FALSE,xlab=NA,ylab=NA)

```

with the "Knit HTML" button of RStudio then the caption does not appear in the html output file. Indeed the html source code corresponding to the figure is:

<p><img src="data:image/png;base64,..." alt="mycaption"/></p> 

To see the caption it should be for instance:

<p><img src="data:image/png;base64,..." alt="mycaption"/><p class="caption">mycaption</p></p> 

How to easily get an html output with visible captions ?

Answer 1

I usually just use results='asis' in the chunk options and include raw html in the chunk, wrapping it in cat() but as Yihui mentioned you can create your own hook:

```{r}
knit_hooks$set(htmlcap = function(before, options, envir) {
  if(!before) {
    paste('<p class="caption">',options$htmlcap,"</p>",sep="")
    }
    })
```

```{r, htmlcap="Hello Dolly"}
library(ggplot2)
ggplot(diamonds,aes(price,carat)) + geom_point()
```