A student asked me about how to include summary results in the abstract or executive summary at the top of an R Markdown report when they don’t get calculated until somewhere below.
I feel like I’ve seen a generally accepted solution to this, but I can’t find it. I thought maybe Keith Baggerly mentioned this in his slides about good reproducible reports, but he doesn’t seem to. I did find this RStudio Community discussion that is relevant, but it doesn’t have quite the solution I would want.
My suggestion was to include a code chunk something like this before the abstract:
```{r load_summary_results, echo=FALSE}
summary_file <- "_cache/summary_results.RData"
if(file.exists(summary_file)) {
load(summary_file)
} else {
resultA <- NA
resultB <- NA
resultC <- NA
}
```
And then use resultA, resultB, and resultC in the abstract.
At the bottom of your document, save the results to a file with something like this:
```{r save_summary_results, echo=FALSE}
resultA <- [some calculation]
resultB <- [some other calculation]
resultC <- [a third calculation]
save(resultA, resultB, resultC, file=summary_file)
```
The first time you compile the report, your abstract would have a
bunch of NA values in it. But then if you compile the report
a second time, you’d pull in the results from the previous run.
Is there a better way? Let me know on twitter.