rmarkdown：递归块评估？

Question

我想重新评估rmarkdown文档中R块产生的字符串-可以吗？ 为了演示起见，请考虑以下文档：

---
params:
  B: 'test'
---

```{r simple, results='asis', echo=FALSE}
write(params[['B']], file = "")
```

```{r recursive-evaluation-questionmark, results='asis', echo=FALSE}
write(
  "How to get \"params[['B']]\" evaluated here? This \"`r params[['B']]`\" is
    expected to be \"test\" ...",
  file = "")
```

当前，编织时产生以下内容：

test

How to get “params[[‘B’]]” evaluated here? This “r params[['B']]” is expected to be “test” …

但我想要：

test

How to get “params[[‘B’]]” evaluated here? This “test” is expected to be “test” …

Answer 1

您不能让knitr将R代码视为文本，但是可以使用纯R代码解决该问题。 我还建议使用cat()而不是write() 。 例如，

write(
  paste0("How to get \"params[['B']]\" evaluated here? This \"", params[['B']], "\" is
  expected to be \"test\" ..."),
 file = "")

或更简单

cat("How to get \"params[['B']]\" evaluated here? This \"", params[['B']], "\" is
  expected to be \"test\" ...", sep = "")

对于更复杂的类似宏的替换，您可能需要使用sub()或gsub()函数，例如

msg <- "How to get \"params[['B']]\" evaluated here? This \"%param%\" is
  expected to be \"test\" ..."
cat(sub("%param%", params[['B']], msg))