NOTE: This is the same solution I posted in the knitr google group.
To get rCharts to work with knit2html, you will need to use the print method with the argument include_assets = TRUE. This is because knitr will not add the js and css assets required by an rCharts plot automatically. Here is a minimal working example.
## MorrisJS with Knit2HTML
```{r results = 'asis', comment = NA}
require(rCharts)
data(economics, package = 'ggplot2')
econ <- transform(economics, date = as.character(date))
m1 <- mPlot(x = 'date', y = c('psavert', 'uempmed'), type = 'Line',
data = econ)
m1$set(pointSize = 0, lineWidth = 1)
m1$print('chart2', include_assets = TRUE)
```
Note that you need to use m1$print('chart2', include_assets = TRUE, cdn = TRUE)
if you intend to publish your chart on RPubs, for otherwise the JS and CSS assets will be served from your local library.
Hope this helps.