我想获取R中要使用的knitr函数的示例代码。可能有一种简单的方法，但尝试使用helpExtract函数可以从here（由@AnandaMahto编写）获得以下代码（将高度赞赏共享任何其他有效代码）。根据我的方法，我必须查看函数是否具有示例，并且必须仅包含具有示例的函数。这是非常低效和天真的方法。现在我试图只包含那些有例子的函数。我尝试了以下代码，但它没有按预期工作。如果有人帮我弄清楚如何从R包中提取示例代码，我将非常感激。在此先感谢您的帮助。
\documentclass{book}
\usepackage[T1]{fontenc}
\begin{document}
<< label=packages, echo=FALSE>>=
library(ggplot2)
library(devtools)
source_gist("https://gist.github.com/mrdwab/7586769")
library(noamtools) # install_github("noamtools", "noamross")
@
\chapter{Linear Model}
<< label = NewTest1, results="asis">>=
tryCatch(
{helpExtract(lm, section="Examples", type = "s_text");
cat(
"\\Sexpr{
knit_child(
textConnection(helpExtract(lm, section=\"Examples\", type = \"s_text\"))
, options = list(tidy = FALSE, eval = TRUE)
)
}", "\n"
)
}
, error=function(e) FALSE
)
@
\chapter{Modify properties of an element in a theme object}
<< label = NewTest2, results="asis">>=
tryCatch(
{helpExtract(add_theme , section="Examples", type = "s_text");
cat(
"\\Sexpr{
knit_child(
textConnection(helpExtract(add_theme , section=\"Examples\", type = \"s_text\"))
, options = list(tidy = FALSE, eval = TRUE)
)
}", "\n"
)
}
, error=function(e) FALSE
)
@
\end{document}
答案 0 :(得分：2)
我已经做了一些修改功能的快速工作（我已经包含at this Gist）。 Gist还包含一个示例Rnw文件（我还没有机会检查Rmd文件）。
该功能现在如下所示：
helpExtract <- function(Function, section = "Usage", type = "m_code", sectionHead = NULL) {
A <- deparse(substitute(Function))
x <- capture.output(tools:::Rd2txt(utils:::.getHelpFile(utils::help(A)),
options = list(sectionIndent = 0)))
B <- grep("^_", x) ## section start lines
x <- gsub("_\b", "", x, fixed = TRUE) ## remove "_\b"
X <- rep(FALSE, length(x)) ## Create a FALSE vector
X[B] <- 1 ## Initialize
out <- split(x, cumsum(X)) ## Create a list of sections
sectionID <- vapply(out, function(x) ## Identify where the section starts
grepl(section, x[1], fixed = TRUE), logical(1L))
if (!any(sectionID)) { ## If the section is missing...
"" ## ... just return an empty character
} else { ## Else, get that list item
out <- out[[which(sectionID)]][-c(1, 2)]
while(TRUE) { ## Remove the extra empty lines
out <- out[-length(out)] ## from the end of the file
if (out[length(out)] != "") { break }
}
switch( ## Determine the output type
type,
m_code = {
before <- "```r"
after <- "```"
c(sectionHead, before, out, after)
},
s_code = {
before <- "<<eval = FALSE>>="
after <- "@"
c(sectionHead, before, out, after)
},
m_text = {
c(sectionHead, paste(" ", out, collapse = "\n"))
},
s_text = {
before <- "\\begin{verbatim}"
after <- "\\end{verbatim}"
c(sectionHead, before, out, after)
},
stop("`type` must be either `m_code`, `s_code`, `m_text`, or `s_text`")
)
}
}
发生了什么变化？
sectionHead。这用于能够在helpExtract函数的调用中指定节标题。 ""（不会打印）。使用示例如下：
<<echo = FALSE>>=
mySectionHeading <- "\\section{Some cool section title}"
@
\Sexpr{knit_child(textConnection(
helpExtract(cor, section = "Examples", type = "s_code",
sectionHead = mySectionHeading)),
options = list(tidy = FALSE, eval = FALSE))}
注意：由于Sexpr不允许使用大括号（{），因此我们需要在Sexpr步骤之外指定标题，我已经完成了在一个隐藏的代码块中。
答案 1 :(得分：1)
这不是一个完整的答案所以我将其标记为社区维基。下面是两个简单的行，用于从命名函数的Rd文件中获取示例（在本例中为lm）。在我看来，代码比Ananda的要点简单得多：
x <- utils:::.getHelpFile(utils::help(lm))
sapply(x[sapply(x, function(z) attr(z, "Rd_tag") == "\\examples")][[1]], `[[`, 1)
结果是Rd“examples”部分中所有文本的简单向量，应该很容易解析，评估或包含在knitr doc中。
[1] "\n"
[2] "require(graphics)\n"
[3] "\n"
[4] "## Annette Dobson (1990) \"An Introduction to Generalized Linear Models\".\n"
[5] "## Page 9: Plant Weight Data.\n"
[6] "ctl <- c(4.17,5.58,5.18,6.11,4.50,4.61,5.17,4.53,5.33,5.14)\n"
[7] "trt <- c(4.81,4.17,4.41,3.59,5.87,3.83,6.03,4.89,4.32,4.69)\n"
[8] "group <- gl(2, 10, 20, labels = c(\"Ctl\",\"Trt\"))\n"
[9] "weight <- c(ctl, trt)\n"
[10] "lm.D9 <- lm(weight ~ group)\n"
[11] "lm.D90 <- lm(weight ~ group - 1) # omitting intercept\n"
[12] "\n"
[13] "\n"
[14] "opar <- par(mfrow = c(2,2), oma = c(0, 0, 1.1, 0))\n"
[15] "plot(lm.D9, las = 1) # Residuals, Fitted, ...\n"
[16] "par(opar)\n"
[17] "\n"
[18] "\n"
[19] "### less simple examples in \"See Also\" above\n"
答案 2 :(得分：1)
也许以下内容可能有用。
get.examples <- function(pkg=NULL) {
suppressWarnings(f <- unique(utils:::index.search(TRUE, find.package(pkg))))
out <- setNames(sapply(f, function(x) {
tf <- tempfile("Rex")
tools::Rd2ex(utils:::.getHelpFile(x), tf)
if (!file.exists(tf)) return(invisible())
readLines(tf)
}), basename(f))
out[!sapply(out, is.null)]
}
ex.base <- get.examples('base')
这将返回指定的包向量中所有函数（包含示例的文档）的示例。如果是pkg=NULL，则返回已加载包中所有函数的示例。
例如：
ex.base['scan']
# $scan
# [1] "### Name: scan"
# [2] "### Title: Read Data Values"
# [3] "### Aliases: scan"
# [4] "### Keywords: file connection"
# [5] ""
# [6] "### ** Examples"
# [7] ""
# [8] "cat(\"TITLE extra line\", \"2 3 5 7\", \"11 13 17\", file = \"ex.data\", sep = \"\\n\")"
# [9] "pp <- scan(\"ex.data\", skip = 1, quiet = TRUE)"
# [10] "scan(\"ex.data\", skip = 1)"
# [11] "scan(\"ex.data\", skip = 1, nlines = 1) # only 1 line after the skipped one"
# [12] "scan(\"ex.data\", what = list(\"\",\"\",\"\")) # flush is F -> read \"7\""
# [13] "scan(\"ex.data\", what = list(\"\",\"\",\"\"), flush = TRUE)"
# [14] "unlink(\"ex.data\") # tidy up"
# [15] ""
# [16] "## \"inline\" usage"
# [17] "scan(text = \"1 2 3\")"
# [18] ""
# [19] ""
# [20] ""
# [21] ""