在.Rmd文件中使用Knitr有条件地评估标题 [英] Conditionally evaluate heading using knitr in .Rmd file

问题描述

是否可以使用R Markdown和knitr有条件地评估代码块及其关联的标题?例如，如果eval_cell是TRUE，则包括块及其，但如果eval_cell是FALSE，则不包括块.

Is it possible to conditionally evaluate a code chunk and its associated heading using R Markdown and knitr? For example, if eval_cell is TRUE include the chunk and its heading, but don't include either if eval_cell is FALSE.

```{r}
eval_cell = TRUE
```

# Heading (would like to eval only if eval_cell is TRUE)
```{r eval = eval_cell}
summary(cars)
```

推荐答案

您可以将标题放入内联R表达式中:

You can put the heading in an inline R expression:

```{r}
eval_cell = TRUE
```

`r if (eval_cell) '# Heading (would like to eval only if eval_cell is TRUE)'`

```{r eval = eval_cell}
summary(cars)
```

如果需要有条件地包含大量文本/代码，这将变得很麻烦，在这种情况下，建议您将它们放在单独的子文档中，例如child.Rmd:

This will become cumbersome if you have large blocks of text/code that need to be conditionally included, in which case you are recommended to put them in a separate child document, say, child.Rmd:

# Heading (would like to eval only if eval_cell is TRUE)
```{r}
summary(cars)
```

然后，您只需要在原始(父)文档中

Then in the original (parent) document, you just need

```{r}
eval_cell = TRUE
```

```{r child='child.Rmd', eval=eval_cell}
```

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