Conditionally display block of markdown text using knitr

Question

I would like to edit a single rmarkdown (Rmd) document with a list of \"problems\", each followed by its solution. Each solution may contain the results of R console, but al

Answer 1

There is a way to hide parts of the document (including text and chunks): to comment them out with html comment marks.

And comment marks can be generated by R in a block according to a variable that can be set at the beginning of the document.

```{r results='asis', echo=FALSE}
if (hide) {cat("")}
```

And just to show a complete working example, in the example below the middle section of the document can be shown or hidden by setting the hide variable to FALSE or TRUE. That might be useful in case there are several sections to hide or show at once - for example, solutions of course problems.

---
title: "Untitled"
date: "15/10/2020"
output:
  word_document: default
  html_document: default
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
hide <- TRUE #TRUE to comment out part of the document, FALSE to show.
```

## Start

Always shown.

```{r}
hide
```

```{r results='asis', echo=FALSE}
if (hide) {cat("")}
```



## End

Always shown.