Cannot output markdown report from Shiny app - html

Question

I have created quite a long and complicated shiny app, which produces tables and plots based on various user inputs. I want to create a 'download report' button which will display the charts and plots currently visible on the app.
However, I cannot seem to produce a report that works. I have used an example shiny app which contains my problem, hoping that there is a simple solution. When I click 'download report', it asks me to select the save location and produces a report called 'report'. However, it is not an HTML format. It does not have any format actually, so I cannot open it and view the results
Shiny app:
#install.packages("shiny")
library(shiny)
library(ggplot2)
ui <- fluidPage(
title = 'Example application',
sidebarLayout(
sidebarPanel(
helpText(),
selectInput('x', 'Build a regression model of mpg against:',
choices = names(mtcars)[-1]),
radioButtons('format', 'Document format', c('PDF', 'HTML', 'Word'),
inline = TRUE),
downloadButton('downloadReport')
),
mainPanel(
plotOutput('regPlot')
)
)
)
server <- function(input, output) {
chart1 <- reactive({
ggplot(data = mtcars, aes(x=input$x, y=mpg))+geom_point()
})
output$regPlot <- renderPlot({
chart1()
})
output$downloadReport <- downloadHandler(
filename = function() {
paste('my-report', sep = '.', switch(
input$format, PDF = 'pdf', HTML = 'html', Word = 'docx'
))
},
content = function(file) {
src <- normalizePath('report.Rmd')
owd <- setwd(tempdir())
on.exit(setwd(owd))
file.copy(src, 'report.Rmd', overwrite = TRUE)
library(rmarkdown)
out <- render('report.Rmd', switch(
input$format,
PDF = pdf_document(), HTML = html_document(), Word = word_document()
))
file.rename(out, file)
}
)
}
shinyApp(ui=ui, server=server)
R Markdown file:
---
title: "Download report"
author: "Test"
date: "24 October 2017"
output: html_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
library(ggplot2)
library(shiny)
library(rmarkdown)
```
## Output plot
Should output plot, here:
```{r test plot, echo=FALSE}
chart1()
```
I must be missing something simple here!

Answer 1

The solution was very simple, but might help others.
The default setting in my Shiny app was to 'Run in Window' when used. However, simply changing this to 'Run External' allowed me to download reports as desired.
Hope this helps someone!