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

I want to extract the example code from an R package and run it in an rmarkdown file automatically.

I am able to extract the code using the function utils::example as follows.

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

I have tried to use chunk options results="asis" as follows, but the result is given as code output rather than code chunk.

```{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("```")
```

I would like to have the code as a code block and the output from the same as in http://ggplot2.tidyverse.org/reference/geom_histogram.html . How to achieve this?

Answer 1

Updated answer:

You can create a function to extract code and use it as a code argument in chunk option.

# 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)]
}

Your Rmd ( myFile.Rmd ) should look like this:

 ```{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)} ``` 

Knit Rmd with: knitr::knit2html("myFile.Rmd") for a result like this:

---

Previous answer:

Write extracted code to a dummy file ( foo.R ) and use it as a code argument in chunk option.

Example file ( myFile.Rmd ):

• First chunk: loads tested library
• Second chunk: extracts example and saves it to a file
• Third chunk: runs extracted code

 ```{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")} ``` 

knit file with knitr::knit2html("myFile.Rmd") for a result like this:

We can also remove hard-coded variables to have a more flexible output:

 ```{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")} ```