Generate Markdown Comments Within for Loop

generate markdown comments within for loop

I think you can obtain what you want in knitr with the code chunk option results='asis' that you can specify after "#+" in an R script to be passed to spin (but the code looks less "clean" than the interesting brew solution proposed by @daroczig):

#+ results='asis', echo = FALSE
for (i in 1:5) {
    cat("## This is a heading for ", i, "\n")
    cat("<!-- This is a comment for ", i, "-->\n")
    print(i)    
}

If this is test.R script and that you do spin("test.R"), the resulting md file will look like that :

## This is a heading for  1 
<!-- This is a comment for  1 -->
[1] 1
## This is a heading for  2 
<!-- This is a comment for  2 -->
[1] 2
## This is a heading for  3 
<!-- This is a comment for  3 -->
[1] 3
## This is a heading for  4 
<!-- This is a comment for  4 -->
[1] 4
## This is a heading for  5 
<!-- This is a comment for  5 -->
[1] 5

Print r comments in a loop in markdown

No need to try to print comment in my opinion. You can use cat("this is the number", i, "\n") within your loop. Eg:

for (i in 1:5)
  cat("this is number", i, "\n")

this is number 1 
this is number 2 
this is number 3 
this is number 4 
this is number 5 

message instead of cat, tends to be preferred as we can easily get rid of them with suppressMessages or, better, message=FALSE in knitr/rmarkdown chunks.

Creating R Markdown htmls by looping

The link you mention gives all the elements to generate a parametrized report.

On your example, you could knit with custom parameters using rmarkdown::render.

markdown file : test.Rmd

---
title: "Create markdown htmls with loop"
author: "Nathan Roe"
date: "2/17/2022"
output: html_document
params: 
  letter: 'a'
---


# `r paste('Processing letter ',letter)`

```{r}
letter
```

html file generation with loop :

for (letter in letters[1:5] ) {
  rmarkdown::render(input = 'test.Rmd',
                    output_file = paste0(letter,".html"), 
                    params = list(letter = letter))
}

...

R markdown: Use for loop to generate text and display figure/table

You can use result = 'asis' inside the r chunk and use cat() to create the sections.

---
title: "R Notebook"
output:
  html_document
---

## Example

```{r, results='asis'}
require(ggplot2)
for(i in 1:5){
  cat("### Section ", i, "\n")
  
  df <- mtcars[sample(5),]
  tb <- knitr::kable(df, caption = paste0("Table",i))
  g1 <- ggplot2::ggplot(df, aes(x = mpg, y = disp, fill = gear)) +
    ggplot2::geom_point() +
    ggplot2::labs(title = paste0("Figure ", i))
  cat("\n")
  print(g1)
  print(tb)
  cat("\n")
}
```

R Markdown, output test results in loop

Solution Type 1

You could do a capture.output(cat(.)) approach with some lapply-looping. Send the output to a file and use rmarkdown::render(.).

This is the R code producing a *.pdf.

capture.output(cat("---
title: 'Test Results'
author: 'Tom & co.'
date: '11 10 2019'
output: pdf_document
---\n\n```{r setup, include=FALSE}\n
knitr::opts_chunk$set(echo = TRUE)\n
mtcars <- data.frame(mtcars)\n```\n"), file="_RMD/Tom.Rmd")  # here of course your own data

lapply(seq(mtcars), function(i) 
  capture.output(cat("# Model", i, "\n\n```{r chunk", i, ", comment='', echo=FALSE}\n\
                   print(summary(lm(mpg ~ ", names(mtcars)[i] ,", mtcars)))\n```\n"),
                 file="_RMD/Tom.Rmd", append=TRUE))

rmarkdown::render("_RMD/Tom.Rmd")

Produces:

Solution Type 2

When we want to automate the output of multiple model summaries in the rmarkdown itself, we could chose between 1. selecting chunk option results='asis' which would produce code output but e.g. # Model 1 headlines, or 2. to choose not to select it, which would produce Model 1 but destroys the code formatting. The solution is to use the option and combine it with inline code that we can paste() together with another sapply()-loop within the sapply() for the models.

In the main sapply we apply @G.Grothendieck's venerable solution to nicely substitute the Call: line of the output using do.call("lm", list(.)). We need to wrap an invisible(.) around it to avoid the unnecessary sapply() output [[1]] [[2]]... of the empty lists produced.

I included a ". " into the cat(), because leading white space like ` this` will be rendered to this in lines 6 and 10 of the summary outputs.

This is the rmarkdown script producing a *pdf that can also be executed ordinary line by line:

---
title: "Test results"
author: "Tom & co."
date: "15 10 2019"
output: pdf_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```
# Overview

This is an example of an ordinary code block with output that had to be included.

```{r mtcars, fig.width=3, fig.height=3}
head(mtcars)
```
# Test results in detail

The test results follow fully automated in detail.

```{r mtcars2, echo=FALSE, message=FALSE, results="asis"}
invisible(sapply(tail(seq(mtcars), -2), function(i) {
  fo <- reformulate(names(mtcars)[i], response="mpg")
  s <- summary(do.call("lm", list(fo, quote(mtcars))))
  cat("\n## Model", i - 2, "\n")
  sapply(1:19, function(j) 
    cat(paste0("`", ". ", capture.output(s)[j]), "`  \n"))
  cat("  \n")
  }))
```

***Note:*** This is a concluding remark to show that we still can do other stuff afterwards.

Produces:

(Note: Site 3 omitted)

how to create a loop that includes both a code chunk and text with knitr in R

You can embed the markdown inside the loop using cat().

Note: you will need to set results="asis" for the text to be rendered as markdown.
Note well: you will need two spaces in front of the \n new line character to get knitr to properly render the markdown in the presence of a plot out.

# Monthly Air Quality Graphs
```{r pressure,fig.width=6,echo=FALSE,message=FALSE,results="asis"}

attach(airquality)
for(i in unique(Month)) {
  cat("  \n###",  month.name[i], "Air Quaility  \n")
  #print(plot(airquality[airquality$Month == i,]))
  plot(airquality[airquality$Month == i,])
  cat("  \n")
}
```

R Markdown - format text as a header in a loop seems to be working for 1st loop iteration only

I don't know why this works, but try one line instead of three:

cat("\n\n### ", experiment_names[id], "\n")

---

Related Topics