How to run scripts by selecting them from a dropdown menu in R Shiny app?

Question

I am trying to create a shiny app where the user selects an R Markdown file from a drop down menu, and that file is then rendered in the app and the output of that file, a pdf file pops up.

I don't have trouble making a drop down menu, but I am struggling with how to code all of that in the server side of the script.

How would I be able to get a Shiny app to render an R markdown file from a drop down menu? Any help is appreciated.

Answer 1

As discussed in comments:

library(shiny)
shinyApp(
  ui = fluidPage(
    selectInput("report", "Report", choices=c('Report1.Rmd','Report2.Rmd')),
    downloadButton("report", "Generate report")
  ),
  server = function(input, output) {
    output$report <- downloadHandler(
      # For PDF output, change this to "report.pdf"
      filename = "report.html",
      content = function(file) {
        # Set up parameters to pass to Rmd document
        params <- list(n = 1)
        
        rmarkdown::render(input$report, output_file = file,
                          params = params,
                          envir = new.env(parent = globalenv())
        )
      }
    )
  }
)

The .Rmd files should be in the working directory.

For example: Report1.Rmd

title: "Dynamic report 1"
output: html_document
params:
  n: NA
---

```{r}
# The `params` object is available in the document.
params$n
```

A plot1 of `params$n` random points.

```{r}
plot(rnorm(params$n), rnorm(params$n))
```