This small RMarkdown files demonstrates the knitr chunk label prefix cache problem

knitr_cache_issue

knitr cache problem
========================================================

This markdown doc demonstrates the problem.  I am using R 3.0.2 (in RStudio, if it matters) and knitr 1.5.

```{r libs}
library(knitr)
opts_chunk$set(cache=TRUE, autodep=TRUE)
library(ggplot2)
```


```{r define_function}
make_plot_data<-function(num) { return(data.frame(x=rnorm(num))) }
```

The `plot_data` chunk will not be cached.  Apparently because there is another chunk named `plot`, which is a prefix match of `plot_data`.

```{r plot_data}
the_data<-make_plot_data(1000000)
```

```{r plot}
ggplot(the_data, aes(x))+geom_density()
```


```{r more_data}
other_data<-make_plot_data(1000000)
```

```{r not_a_prefix_match_of_more_data}
ggplot(other_data, aes(x))+geom_density()
```