[英]Print custom object in rmarkdown and knitr (PDF and HTML)
Let's say I have a package with a function that returns an S3 object: 假设我有一个带有返回S3对象的函数的包:
new_myclass <- function() {
return(structure(list(a=1, b=2), class = "myclass"))
}
I also have two functions that take a myclass
object and return respectively a HTML representation and a LaTeX representation of the object. 我也有两个函数,它们带有一个myclass
对象,并分别返回该对象的HTML表示形式和LaTeX表示形式。
myclass2html <- function(obj) { return("<p>MyClass object</p>")}
myclass2latex <- function(obj) { return("\begin{em}MyClass\end{em} object $x$")}
What functions/methods should I define to provide consistent and transparent knitr
and rmarkdown
support? 我应该定义哪些函数/方法来提供一致和透明的knitr
和rmarkdown
支持? I would like to support both .Rmd
files and .R
files with a header like: 我想同时支持.Rmd
文件和.R
文件,其标题如下:
#'---
#' title: My document
#' output: pdf_output
#'---
So far my approach goes through the knit_print
method: 到目前为止,我的方法是通过knit_print
方法进行的:
knit_print.myclass <- function(x, ...) {
rmarkdown_fmt <- rmarkdown::metadata$output
knitr_fmt <- knitr::opts_knit$get("out.format")
# should I use these heuristics with both variables?
if (rmarkdownfmt == "pdf_document") {
return(knitr::asis_output(myclass2latex(x)))
}
if (knitr_fmt %in% c("html", "markdown")) {
return(knitr::asis_output(myclass2html(x)))
} else {
stop("Format not supported!")
}
}
My main issue is that there may be two variables rmarkdown::metadata$output
and knitr::opts_knit$get("out.format")
that may or may not be defined (depending on whether or not rmarkdown
is being used). 我的主要问题是可能存在或可能rmarkdown::metadata$output
两个变量rmarkdown::metadata$output
和knitr::opts_knit$get("out.format")
(取决于是否使用rmarkdown
)。 I find this confusing. 我觉得这很混乱。
knit_print
the right method to customize for this purpose? knit_print
是否是为此目的定制的正确方法? get_output_format
function that tells me the output format? 是否有一个get_output_format
函数可以告诉我输出格式? To put the question in context, I am working on the condformat package that allows to visualize DataFrames with conditional formatting rules. 为了解决这个问题,我正在研究condformat包,该包允许使用条件格式设置规则可视化DataFrame。
EDIT: So far I have been doing my own voodoo to detect the output format: 编辑:到目前为止,我一直在做我自己的伏都教以检测输出格式:
#' @importFrom rmarkdown metadata
#' @importFrom knitr opts_knit
guess_output_format <- function() {
rmd_output <- tryCatch({rmarkdown::metadata$output},
error = function(e) {NULL})
if (is.null(rmd_output)) {
rmd_output = ""
}
if (is.list(rmd_output)) {
rmd_output <- names(rmd_output)[1]
}
if (rmd_output == "pdf_document") {
return("latex")
} else if (rmd_output %in% c("html_document", "html_vignette")) {
return("html")
} else if (rmd_output != "") {
stop("Unsupported rmarkdown output format:", rmd_output)
}
# No rmarkdown, let's try with knitr:
format <- knitr::opts_knit$get("out.format")
if (format %in% c("html", "markdown")) {
return("html")
} else if (format %in% c("latex")) {
return("latex")
} else {
stop("Format not supported!")
}
}
EDIT : Further discussion here: https://github.com/rstudio/rmarkdown/issues/649 编辑 :这里有进一步的讨论: https : //github.com/rstudio/rmarkdown/issues/649
With knitr 1.18 this is much simpler: 使用knitr 1.18,这要简单得多:
guess_output_format <- function() {
if (knitr::is_html_output()) {
return("html")
} else if (knitr::is_latex_output()) {
return("latex")
} else {
return("unsupported")
}
}
Related issue: https://github.com/rstudio/rmarkdown/issues/649 相关问题: https : //github.com/rstudio/rmarkdown/issues/649
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