代码如下 ## Slide 2
```{r}
library(ggplot2)
g <- ggplot(cars, aes(speed, dist))
g + geom_point() +
    geom_smooth()


错误
> slidify("index.Rmd")


processing file: index.Rmd
  |......................                                           |  33%
  ordinary text without R code

  |...........................................                      |  67%
label: unnamed-chunk-1
Quitting from lines 24-28 (index.Rmd)
Error in evaluate(code, envir = env, new_device = FALSE, keep_warning = !isFALSE(options$warning),  :
  could not find function "parse_all"
```