Loop to auto build flexdashboard content, specifically columns with tabs where each tab is an htmlwidget (like highcharts). Be sure to look at the raw code.

auto-tab-flexdashboard.Rmd

---
title: "Loop to Auto Build Tabs Containing htmlwidgets"
output: flexdashboard::flex_dashboard
---

```{r setup, echo =FALSE, eval = TRUE}
library(tidyverse)
library(flexdashboard)
library(highcharter)

labels <- mtcars %>% names # these will serve as labels for each tab

# create a bunch of random, nonsensical line graphs
hcs <- purrr::map(.x = mtcars, ~highcharter::hchart(mtcars, y = .x, type = 'line')) %>%
    setNames(labels) # assign names to each element to use later as tab titles
```

Page
====================

Column {.tabset .tabset-fade}
-----------------------------

<!-- loop to build each tabs (in flexdashboard syntax) -->
<!-- each element of the list object `out` is a single tab written in rmarkdown -->
<!-- you can see this running the next chunk and typing `cat(out[[1]])` -->

```{r, echo = FALSE, eval = TRUE}

out <- lapply(seq_along(hcs), function(i) {

  a1 <- knitr::knit_expand(text = sprintf("### %s\n", names(hcs)[i])) # tab header, auto extracts names of `hcs`
  a2 <- knitr::knit_expand(text = "\n```{r}") # start r chunk
  a3 <- knitr::knit_expand(text = sprintf("\nhcs[[%d]]", i)) # extract graphs by "writing" out `hcs[[1]]`, `hcs[[2]]` etc. to be rendered later
  a4 <- knitr::knit_expand(text = "\n```\n") # end r chunk

  paste(a1, a2, a3, a4, collapse = '\n') # collapse together all lines with newline separator

})

```

<!-- source: https://goo.gl/fnfXuO -->
<!-- As I mentioned in the SO post, I don't quite understand why it has to be -->
<!-- 'r paste(knitr::knit(...)' sometimes vs 'r knitr::knit(...)' but oh well -->

`r knitr::knit(text = paste(out, collapse = '\n'))`