从 R 包函数中检索并执行示例代码作为 R-markdown 中的代码块

Question

我想从 R 中提取示例代码打包并在 rmarkdown 中运行自动归档。

我可以使用函数 utils::example 提取代码如下。

example("geom_histogram", package = "ggplot2", ask = F,
         prompt.prefix = "", give.lines = TRUE)[-(1:5)]

我尝试使用 block 选项 results="asis"如下，但结果是作为代码输出而不是代码块给出的。

```{r,echo = FALSE, results="asis"}
cat("```{r}")
library(ggplot2)
cat(paste(example("geom_histogram", package = "ggplot2", ask = F,
                  prompt.prefix = "", give.lines = TRUE)[-(1:5)], collapse = "\n"))
cat("```")
```

我想将代码作为代码块，输出与 http://ggplot2.tidyverse.org/reference/geom_histogram.html 中的相同.如何做到这一点？

Answer 1

更新答案:

您可以创建一个函数来提取代码并将其用作 code block 选项中的参数。

# Function saved in functions.R file
getCode <- function(myFunction, myPackage) {
    example(myFunction, myPackage, ask = FALSE, character.only = TRUE,
            prompt.prefix = "", give.lines = TRUE)[-(1:5)]
}

您的 Rmd ( myFile.Rmd ) 应如下所示:

```{r, meta, include = FALSE}
myPackage  <- "ggplot2"
myFunction <- "geom_histogram"
source("functions.R")
```

```{r, intro, echo = FALSE, results = "asis"}
cat("#", myPackage, "\n")
cat("##", myFunction, "\n")
library(myPackage, character.only = TRUE)
```

```{r, runCode, code = getCode(myFunction, myPackage)}
```

针织 Rmd与: knitr::knit2html("myFile.Rmd")对于这样的结果:



上一个答案:

将提取的代码写入一个虚拟文件( foo.R )并将其用作 code block 选项中的参数。

示例文件( myFile.Rmd):

第一个 block :加载测试库

第二 block :提取示例并将其保存到文件

第三 block :运行提取的代码

```{r, meta, include = FALSE}
library(ggplot2)
```

```{r, getCode, include = FALSE}
code <- example("geom_histogram", package = "ggplot2", ask = FALSE,
                prompt.prefix = "", give.lines = TRUE)[-(1:5)]
write.table(code, "foo.R", quote = FALSE, row.names = FALSE, col.names = FALSE)
```

```{r, runCode, code = readLines("foo.R")}
```

使用 knitr::knit2html("myFile.Rmd") 编织文件对于这样的结果:



我们还可以删除硬编码的变量以获得更灵活的输出:

```{r, meta, include = FALSE}
myPackage  <- "ggplot2"
myFunction <- "geom_histogram"
library(myPackage, character.only = TRUE)
```

```{r, getCode, include = FALSE}
code <- example(myFunction, myPackage, ask = FALSE, character.only = TRUE,
                prompt.prefix = "", give.lines = TRUE)[-(1:5)]
write.table(code, "foo.R", quote = FALSE, row.names = FALSE, col.names = FALSE)
```

```{r, intro, echo = FALSE, results = "asis"}
cat("#", myPackage, "\n")
cat("##", myFunction, "\n")
```

```{r, runCode, code = readLines("foo.R")}
```