Creating dynamic tabs in Rmarkdown - r

Question

In Rmarkdown, it's possible to create tabs, for example:
---
output: html_document
---
# Tabs {.tabset}
## Tab 1
foo
## Tab 2
bar
I'm wondering if it's possible to create an arbitrary number of tags? How can I create a tab programatically?
The following code is a poor attempt to do this, but it results in a heading instead of a tab.
---
output: html_document
---
# Tabs {.tabset}
```{r echo=FALSE}
shiny::tags$h2("Tab 1")
```
foo
## Tab 2
bar
Solution
Thanks to #GGamba for providing a great solution. I needed to go one step further and be able to add tabs as part of a loop, so I needed to make two changes. First of all, I used this code to dynamically add tabs (the only difference here is that I force the evaluation of hrefCode inside the timeout because otherwise all timeouts called together will use the same value)
(function(hrefCode){setTimeout(function(){
var tabContent = document.createElement('div');
var tabContainerTarget = document.getElementsByClassName('tab-content')[0];
tabContent.setAttribute('id', 'tab-' + hrefCode);
tabContent.setAttribute('class', 'tab-pane')
tabContent.innerHTML = '", gsub('\n', '', Panel, fixed = TRUE), "';
tabContainerTarget.appendChild(tabContent);
}, 100);
})(hrefCode);
Secondly, to add tabs in a loop, you can do something like this:
tabsToAdd <- list("tab3" = "hello", "tab4" = "world")
shiny::tagList(lapply(names(tabsToAdd), function(x) {
addToTabset(title = x, tabsetId = 'tbSet1',
tabPanel(x, tabsToAdd[[x]]))
}))

Answer 1

There is also a simple rmarkdown solution to this problem that does not require shiny and/or custom javascript. Does not work for all kinds of R output (see below):
## Tabbed Example {.tabset}
```{r, results = 'asis'}
for (nm in unique(iris$Species)){
cat("### ", nm, "\n")
cat(knitr::knit_print(plot(iris[iris$Species == nm, ])))
cat("\n")
}
```
A more involved method, that first creates a list of raw Rmarkdown code as a list of character vectors, which are then evaluated in a separate (inline) code chunk with knitr::knit(). This works for all kinds of output, not just base plots.
## Tabbed Example ggplot {.tabset}
```{r}
library(ggplot2)
template <- c(
"### {{nm}}\n",
"```{r, echo = FALSE}\n",
"ggplot(iris[iris$Species == '{{nm}}', ], aes(x = Sepal.Length, y = Sepal.Width)) + geom_point()\n",
"```\n",
"\n"
)
plots <- lapply(
unique(iris$Species),
function(nm) knitr::knit_expand(text = template)
)
```
`r knitr::knit(text = unlist(plots))`

Answer 2

As far as I know what you are trying to do is not possible in rmarkdown (but I'd love to stand corrected). But of course we can implement a function to do just that.
I based my answer on this answer by #KRohde, so all the credits goes to him. I just adapted it to work in a simpler markdown document.
The answer is mostly build with JS rather than R, but as the markdown is mostly an HTML I feel JS is a better tool.
Here is the code:
---
output: html_document
---
```{r echo=FALSE, results='asis'}
library(shiny)
addToTabset <- function(title, tabsetId, Panel) {
tags$script(HTML(paste0("
/* Getting the right tabsetPanel */
var tabsetTarget = document.getElementById('", tabsetId, "');
/* Creating 6-digit tab ID and check, whether it was already assigned. */
hrefCode = Math.floor(Math.random()*100000);
/* Creating node in the navigation bar */
var navNode = document.createElement('li');
var linkNode = document.createElement('a');
linkNode.appendChild(document.createTextNode('", title, "'));
linkNode.setAttribute('data-toggle', 'tab');
linkNode.setAttribute('data-value', '", title, "');
linkNode.setAttribute('href', '#tab-' + hrefCode);
navNode.appendChild(linkNode);
tabsetTarget.appendChild(navNode);
setTimeout(function(){
var tabContent = document.createElement('div');
var tabContainerTarget = document.getElementsByClassName('tab-content')[0];
tabContent.setAttribute('id', 'tab-' + hrefCode);
tabContent.setAttribute('class', 'tab-pane')
tabContent.innerHTML = '", gsub('\n', '', Panel, fixed = T), "';
tabContainerTarget.appendChild(tabContent);
}, 100);
")
))
}
```
The code above should stay in a 'setup chunk', as it define an R function to call a JS function that mostly just add the right things to the DOM.
It can then be used when needed, passing the tabPanel title, the 'target' tabset and the normal tabPanel function.
```{r results='asis', echo=FALSE}
shiny::tabsetPanel(id = 'tbSet1',
shiny::tabPanel('Tab 1', 'foo'),
shiny::tabPanel('Tab 2', 'bar')
)
```
```{r results='asis', echo=FALSE}
addToTabset(title = 'Tab 3',
tabsetId = 'tbSet1',
tabPanel(
h1('This is a title'),
actionButton('btn',label = 'Clicky button'),
radioButtons('asd', LETTERS[1:5], LETTERS[1:5])) )
```

Answer 3

This also appears to be a good way to also deal with the problem of dynamic tabsets with plotly graphics at https://github.com/ropensci/plotly/issues/273
I created the plots first and saved them in a list which I then extract and display with a simple code in the template variable below. This saves me from having to enclose the large code in quotes in the template file.
However, if I try this trick a second time in the same document, it complains with a "duplicate chunk label "unnamed-chunk-1"... error and will not compile.
This appears to be "fixable" by specifying options(knitr.duplicate.label = "allow") but are there any "consequences" to allowing duplicate labels that I need to be aware of? I read https://bookdown.org/yihui/rmarkdown-cookbook/duplicate-label.html and I think I'm ok but is there a better way than allowing duplicate chunk labels?
---
title: "Tabsets for plotly graphs"
output:
html_document:
number_sections: yes
toc: yes
toc_depth: 4
---
## Tabbed Set 1 {.tabset}
```{r}
options(knitr.duplicate.label = "allow")
library(plotly)
plotlist <- plyr::dlply(iris, "Species", function(iris.part){
plot_ly(data=iris.part, x = ~Sepal.Length, y = ~Sepal.Width)
})
template <- c(
"### First {{nm}}\n",
"```{r, echo = FALSE}\n",
"plotlist[[{{nm}}]] \n",
"```\n",
"\n"
)
plots <- lapply(1:length(plotlist), function(nm) {knitr::knit_expand(text = template)})
```
`r knitr::knit(text = unlist(plots))`
## Tabbed set 2 {.tabset}
```{r}
library(plotly)
template <- c(
"### Second {{nm}}\n",
"```{r, echo = FALSE}\n",
"plotlist[[{{nm}}]] \n",
"```\n",
"\n"
)
plots <- lapply(1:length(plotlist), function(nm) {knitr::knit_expand(text = template)})
```
`r knitr::knit(text = unlist(plots))`