knit_expand() example

knit_expand_edhec_histograms.Rmd

knit_expand() example
========================================================

```{r, label='setup', include=FALSE}
require(data.table)
require(PerformanceAnalytics)
require(reshape2)
opts_chunk$set(eval=TRUE,echo=FALSE)
data(edhec)
edhec<-data.table(melt(data.frame(date=index(edhec),coredata(edhec)),id.vars='date'))
setkey(edhec,variable,date)
```

```{r, results='asis'}
template = c('## Histogram of {{i}}',
             '```{r}',
             'hist(edhec["{{i}}"]$value)',
             '```')
src = lapply(as.character(unique(edhec$variable)), function(i) {
knit_expand(text=c(template))
})
# knit the source
cat(knit(text = unlist(src), quiet = TRUE))
```

What's the idiomatic way of passing in multiple variables to the template, eg where one or two are fixed value variables, and two others come from a particular row in the original dataframe?