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包中提取示例代码并rmarkdown自动在文件中运行它.

我能够使用utils::example如下函数提取代码.

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

我尝试使用results="asis"如下的块选项,但结果是作为代码输出而不是代码块.

```{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.怎么做到这一点？

Answer 1

更新的答案:

您可以创建一个函数来提取代码并将其用作code块选项中的参数.

# 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)]
}

你的Rmd(myFile.Rmd)应该是这样的:

```{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)}
```

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

上一个答案:

将提取的代码写入虚拟文件(foo.R)并将其用作code块选项中的参数.

示例文件(myFile.Rmd):

• 第一块:加载测试库
• 第二个块:提取示例并将其保存到文件中
• 第三个块: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")}
```

用这样knitr::knit2html("myFile.Rmd")的结果编织文件:

我们还可以删除硬编码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")}
```