Generate Dynamic R Markdown Blocks - r

Question

In my dataset, I have 60 groups that I want to analyze in put into an HTML report using R Markdown. Because I want to apply the same analysis to each group, I am hoping that there is a way I can dynamically generate the code blocks/analysis.
Simply, I want to avoid replicating the block 60 times.
I came across this this question which uses children in knitr. I have attempted to replicate this with the iris dataset. In my example below, all I wanted to do was generate three H4 titles, one for each species.
It's worth noting that I am not married to this approach, it just appears to be related to what I am looking to do.
Here are the files I used:
parent.RMD file. This would be my "master" report.
Automate Chunks of Analysis in R Markdown
========================================================
```{r setup, echo=FALSE}
library(knitr)
```
```{r run-numeric-md, include=FALSE}
out = NULL
for (i in as.character(unique(iris$Species))) {
out = c(out, knit_child('child.Rmd'))
}
```
And here is child.Rmd.
#### Species = `r [i]`

Answer 1

Try knit_expand():
Automate Chunks of Analysis in R Markdown
========================================================
```{r setup, echo=FALSE}
library(knitr)
```
```{r run-numeric-md, include=FALSE}
out = NULL
for (i in as.character(unique(iris$Species))) {
out = c(out, knit_expand(text='#### Species = {{i}}'))
}
```
`r paste(knit(text = out), collapse = '\n')`
You can also create a template file like 'child.rmd' and put this in your for loop so you don't have to put a complicated analysis in quotes:
out = c(out, knit_expand('template.rmd'))
Then have your 'template.rmd' be:
#### Species = {{i}}

Answer 2

Taking #sam's solution, I made the following generic function. Say you have a data frame called grfDf with DiagrammeR graph objects in the column graph. The following is all you need to plot all the graphs in Rmd : r require(DiagrammeR); renderHtmlWidgetList(grfDf$graph, render_graph). See the code for caveats.
```
require(knitr)
#' Render a list of htmlWidgets using various tricks
#'
#' #param widgetList A list of htmlWidget objects to be rendered
#' #param renderFunction The function to render individual widgets. It can be either a name
#' of the rendering function, e.g., "render_graph" in DiagrammeR, or the actual function to
#' be passed to this call.
#' #return The knitted string. This is to be included in the output by using `r renderHtmlWidgetList(...)`;
#' #details This is a collection of various tricks. See the URL citations in the code.
#' Note that this code does alliterate global variables starting with "renderHtmlWidgetList_".
#' You may want to delete them using rm(list = ls(pattern="renderHtmlWidgetList_*")).
#' #examples Inlcude the following in the Rmd directly
#' `r require(DiagrammeR); renderHtmlWidgetList(grfDf$graph, render_graph)`
#'
#' #export
renderHtmlWidgetList <- function(widgetList, renderFunction){
# error checking
stopifnot(is.list(widgetList))
# handles if the renderFunction is actually a function
# http://stackoverflow.com/questions/10520772/in-r-how-to-get-an-objects-name-after-it-is-sent-to-a-function
if(is.function(renderFunction)) {
# convert back to string, because we need to knit it later
renderFunction <- deparse(substitute(renderFunction))
}
stopifnot(is.character(renderFunction) & length(renderFunction)==1)
stopifnot(exists(renderFunction, mode = "function"))
# inject global vars; make sure we have a unique global var name
gVarName<- paste0("renderHtmlWidgetList_", sample(1:10000, 1))
while (exists(gVarName)) {
gVarName<- paste0("renderHtmlWidgetList_", sample(1:10000, 1))
}
# assigning widgetList to a global temp var
# http://stackoverflow.com/questions/5510966/create-a-variable-name-with-paste-in-r
assign(gVarName, widgetList, envir = .GlobalEnv)
# solution from https://gist.github.com/ReportMort/9ccb544a337fd1778179
out <- NULL
knitPrefix <- "\n```{r results='asis', cache=FALSE, echo=FALSE}\n\n"
knitSuffix <- "\n\n```"
for (i in 1:length(widgetList)) {
knit_expanded <- paste0(knitPrefix, renderFunction, "(", gVarName, "[[", i, "]])")
out = c(out, knit_expanded)
}
#invisible(out)
paste(knitr::knit(text = out), collapse = '\n')
}
```