How to write reproducible comment in rmarkdown

Question

Can anyone help in how to write a reproducible comment in Rmarkdown?

For example, we have the data set as shown below:

age	fnlwgt	education_num
39	77516	13
50	83311	13
38	215646	9
53	234721	7

In Rmarkdown report comments are typed using # before the text within code chunk. I want to write a reproducible comment for mean age.

# The average age is 45

Is there any way to write the above comment as reproducible? In case I change the values for age variable, the average value should automatically updated in the comment...

I would be thankful for your kind support.

Regards, Farhan

Where do you want that comment? in the `rmd` code chunk or in the report? If in the report, simply `paste0("The average age is ", mean(df$age))` would do the job. — shafee, Sep 01 '22 at 06:40

shafee · Accepted Answer · 2022-09-01T10:06:49.793

Option 1

One option could be generating the code chunk dynamically using chunk option results="asis".

---
title: "Reproducible comments"
output: html_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

## R Markdown

```{r dt, echo=FALSE}
df <- tibble::tribble(
  ~age, ~fnlwgt, ~education_num,
   39L,  77516L,            13L,
   50L,  83311L,            13L,
   38L, 215646L,             9L,
   53L, 234721L,             7L
  )

```


```{r results="asis", echo=FALSE}
cmnt <- paste0(
"```{r}\n",
"df <- tibble::tribble(
  ~age, ~fnlwgt, ~education_num,
   39L,  77516L,            13L,
   50L,  83311L,            13L,
   38L, 215646L,             9L,
   53L, 234721L,             7L
  )\n\n",
"# The average age is ", mean(df$age), "\n",
"```\n"
)

cat(cmnt)
```

Option 2

Another option could be using knitr::knit_expand to dynamically expand the comments with {{}} in a template r-markdown file.

Suppose this is the template r-markdown file,

template.Rmd


```{r}
mean_age <- mean(dat$age)
# The mean age is {{age}}

mean_educ <- mean(dat$education_num)
# The mean education_num is {{educ}}
```

Now to expand these comments in our main document, we use knitr::knit_expand and pass the variable to be expanded in the comments, and then we add the contents of template.Rmd using knitr::knit_child.

---
title: "Reproducible comments"
output: 
  html_document:
    keep_md: TRUE
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

## R Markdown

```{r}
dat <- tibble::tribble(
  ~age, ~fnlwgt, ~education_num,
   39L,  77516L,            13L,
   50L,  83311L,            13L,
   38L, 215646L,             9L,
   53L, 234721L,             7L
  )
```

## Comments reproduced dynamically

```{r, echo=FALSE, results='asis'}
src = knitr::knit_expand(
  "template.Rmd", 
  age = mean(dat$age), 
  educ = mean(dat$education_num)
)

res = knitr::knit_child(text = src, quiet = TRUE)
cat(res, sep = '\n')
```

I appreciate the response, but the coding is difficult to deal with while drafting a report in its entirety. Is there a straightforward method to go there? — Farhan, Sep 01 '22 at 07:55
@Farhan, see the edited answer. Although I am not sure whether it is a straightforward method. — shafee, Sep 01 '22 at 10:01
I appreciate your prompt reply. Although I think option 1 is more straightforward to execute, both of your alternatives are nice to work with. I believe that in order to fulfil my goals, I may use `cat(paste0("```{r}\n", "# The average age is ", mean(df$age), "\n", "```\n"))` as a comment from option 1. I'm not sure, though, whether there is a simpler method to express this, similar to how we put in reports outside the chunk that says, `The average age is 'r mean(df$age)'`. Isn't it simple :). However, thanks a lot — Farhan, Sep 02 '22 at 11:29

How to write reproducible comment in rmarkdown

1 Answers1

Option 1

Option 2