HTML code inside of a R-markdown block for a single line

问题

I have an R-markdown document in a for loop (testing various kinds of models), and I would like to set them off with HTML Headers, as it is otherwise hard to find the models I am looking for. There is the "asis" option, but that turns off formatting for the entire block, which is not what I want. I have tried a few things I found here, but nothing really works. Here is my code:

---
title: "Untitled"
author: "Mike Wise - 25 Jul 2014"
date: "November 2, 2015"
output: html_document
---

Test

```{r, echo=T}
for (i in 1:3){
  print("<h1>Title</h1>")
  #print("##Title")
  m <- data.frame(matrix(runif(25),5,5))
  print(m)
}
```

Here is one try that does not have the right title formatting:

And here is what it looks like with the results="asis" option:

回答1:

You could try using the kable function:

```{r, echo=T, results="asis"}
library(knitr)
for (i in 1:3){
  print("<h1>Title</h1>")
  #print("##Title")
  m <- data.frame(matrix(runif(25),5,5))
  print(kable(m, format = "html"))
}
```

Which gives me:

回答2:

Try this one.

```{r, echo=F, results="asis"}
for (i in 1:3){
  library(knitr)
  print("<h1>Title</h1>")
  #print("##Title")
  m1 <- knitr::kable(data.frame(matrix(runif(25),5,5)))
  print(m1)
}

```

回答3:

Okay, it is a year and a half later and I still needed this from time to time, but I learned enough since then to know how to do it properly. You need to write a knitr "output hook", and modify the output so the html can "escape" through.

The following accomplishes this:

Added a knitr output hook.
Defined a syntax to specify the needed tag and content
- for example to get <h1>some_text</h1> use htmlesc<<(h1,some_text)>>
Figured out a regexp that extracts the h1 and some_text and reformats it as properly tagged html, removing the ## that knitr inserted as well.
Added some more test cases to make sure it did some additional things (like h4, p, proper placement of plots and tables, etc.)
Added another regexp to remove double escaped lines which was adding some unwanted whitespace paneled constructs.

So here is the code:

---
title: "Output Hook for HTML Escape"
author: "Someone"
date: "2017 M04 25"
output: 
  html_document:
    keep_md: true
---

```{r setup, include=T,echo=TRUE}
knitr::opts_chunk$set(echo = TRUE)
hook_output <- knitr::knit_hooks$get("output")


knitr::knit_hooks$set(output=function(x,options){
  xn <- hook_output(x,options)
  # interestingly xn is a big character string. 
  # I had expected a list or vector, but the length of x is 1 and the class is character.

  # The following regexp extracts the parameters from a statement of the form
  # htmlesc<<(pat1,pat2)>> and converts it to <pat1>pat2</pat1>
  xn <- gsub("## htmlesc<<([^,]*),{1}([^>>]*)>>","\n```\n<\\1>\\2</\\1>\n```\n",xn)
  # now remove double escaped lines that occur when we do these right after each other
  gsub(">\n```\n\n\n```\n<",">\n<",xn)
}
)
```

## An analysis loop in a single R chunk with R Markdown

In the following, we do a loop and generate 3 sets of data:

(@) We have some explanitory text
(@) then we do a bar plot with ggplot
(@) then we print out a table
(@) then we do a base plot - just for fun

```{r, echo=T, fig.height=3,fig.width=5}
library(knitr)
library(tidyr)
library(ggplot2)
set.seed(123)

for (i in 1:3){
  mdf <- data.frame(matrix(runif(25),5,5))
  cat(sprintf("htmlesc<<h1,Title %d>>\n",i))
  cat(sprintf("htmlesc<<h4,Smaller Title - also for %d>>\n",i))
  cat(sprintf("htmlesc<<p,and some text talking about this %d example>>\n",i))
  print(sapply(mdf,mean))
  gdf <- gather(mdf,series,val)
  gp <- ggplot(gdf)+geom_bar(aes(series,val,fill=series,color=I("black")),stat="identity")
  print(gp)
  print(mdf)
  plot(mdf)
}
```

And this is the output (shrunk a bit as you don't need the details).

The only real docs for this by the way are Yihui's excellent knitr book, a search finds it easily.

来源：https://stackoverflow.com/questions/33478874/html-code-inside-of-a-r-markdown-block-for-a-single-line

标签

html

regex

knitr

r-markdown