Where do I save the Rmd file I am generating with a Shiny R App

#1

I have an app to aloter the params argument in an Rmd file and then download said rmd file using the shiny app. Where do I save the rmd file and how do I tell shiny where to look?

This is my app:

setwd("C:/Users/JL16/Documents/Apps/qc-app")
library(shiny)
library(markdown)

 ui = fluidPage(
    textInput("year", "Enter Year"),
    downloadButton("report", "Generate report")
  )
 server <- function(input, output, session) {
   output$report <- downloadHandler(
     filename = "report.html",
     content = function(file) {
       params <- list(year = input$year)
       
       rmarkdown::render("report.Rmd", 
                         output_file = file,
                         params = params,
                         envir = new.env(parent = globalenv())
       )
     }
   )
 }
  
shinyApp(ui, server)
How to I attract help to my tricky Shiny and R Markdown problem? - Using paramterized Rmarkdowns and ShinyR apps/ Interactive markdown files
#2

Maybe https://mastering-shiny.org/action-transfer.html#downloading-reports will help?

#3

For the path you are using, the Rmd file should be in the root folder of your app (the same where the app.R file is located).

Doing this, especially on a Shiny app is a bad idea, the app is going to fail on deployment.
A better workflow would be to create a project for your app, that way you don't need to manually set the working directory.

This simple example works for me

library(shiny)
library(markdown)

ui = fluidPage(
  textInput("year", "Enter Year"),
  downloadButton("report", "Generate report")
)
server <- function(input, output, session) {
  output$report <- downloadHandler(
    filename = "report.html",
    content = function(file) {
      params <- list(year = input$year)
      
      rmarkdown::render("report.Rmd", 
                        output_file = file,
                        params = params,
                        envir = new.env(parent = globalenv())
      )
    }
  )
}

shinyApp(ui, server)

report.Rmd

---
title: "Test"
output: html_document
params:
  year: "2020"
---

```{r}
params$year
```

Rendered report

image
image2211×473 37.8 KB

1 Like
#4

Thanks for the response andresrcs. So when I click generate report it opens a file explorer and asks me to save a file called report but nothing is generated. In the console I get the following error:

Version:1.0 StartHTML:0000000107 EndHTML:0000001754 StartFragment:0000000127 EndFragment:0000001736

Listening on http://127.0.0.1:5494 Warning in normalizePath(path.expand(path), winslash, mustWork) : path[1]="report.Rmd": The system cannot find the file specified Warning: Error in abs_path: The file 'report.Rmd' does not exist. [No stack trace available]

#5

Are you still manually setting the working directory? The issue is self explanatory, Shiny is not being able to find report.Rmd where you are saying it is.

#6

No ive not manually set it this time, getwd() gives me:

"C:/Users/JL16/Documents"

This isn't where the app is stored, my understanding is that shiny should auto detect where my app.R file and report.Rmd file is.

Thanks J