Shiny - download markdown file - shiny

Question

library(shiny)
library(ggplot2)
report.Rmd
date: "2023-01-15"
output: html_document
params:
x_column: "Sepal.Width"
y_column: "Sepal.Length"
library(ggplot2)
ggplot(data = iris)+
aes_string(params$x_column,params$y_column)+
geom_point()
shiny app
library(shiny)
library(ggplot)
library(rmarkdown)
ui <- fluidPage(
titlePanel("Iris Data"),
sidebarLayout(
sidebarPanel(
selectizeInput("xcol",
"Choose X Axis",
choices = names(iris)
),
selectizeInput("ycol",
"Choose Y Axis",
choices = names(iris)
),
downloadButton("project", "Download plot")
),
mainPanel(
plotOutput("plot")
)
)
)
server <- function(input, output) {
filename = "report.html
output$plot <- renderPlot({
ggplot(data=iris)+
aes_string(x=input$xcol, y=input$ycol)+
geom_point()
})
output$print <- downloadHandler({
filename="report.html"
content = function(file) {
rmarkdown::render("report.Rmd",
output_file=file, params=list(x_column = input$xcol,
y_column = input$ycol))
}
})
}
I can't get the app to render my rmarkdown file. I can't seem to see the mistake. report.Rmd is in my working directory. I can get it to work outside of shiny, but in shiny it says there is an error and the content is missing without a default value

Answer 1

There are two issues with your code. First, you used the id Project for the downloadButton but named the output print. Second, the API of downloadHandler is a bit different from reactive or renderXXX, i.e. you have to pass filename and content as arguments.
Note: Also it's good practice to copy the report file to a temporary directory before processing it and to evaluate the document in a child of the global environment. See Generating downloadable reports. As an example where missing the last step fails to render an Rmd correctly see this post. Finally, note that aes_string is deprecated since ggplot2 3.4.0. Instead it's recommended to use the .data pro-noun as I do in the code below.
library(shiny)
library(ggplot2)
ui <- fluidPage(
titlePanel("Iris Data"),
sidebarLayout(
sidebarPanel(
selectizeInput("xcol",
"Choose X Axis",
choices = names(iris)
),
selectizeInput("ycol",
"Choose Y Axis",
choices = names(iris)
),
downloadButton("print", "Download plot")
),
mainPanel(
plotOutput("plot")
)
)
)
server <- function(input, output) {
output$plot <- renderPlot({
ggplot(data = iris) +
aes(.data[[params$x_column]], .data[[params$y_column]]) +
geom_point()
})
output$print <- downloadHandler(
filename = "report.html",
content = function(file) {
tempReport <- file.path(tempdir(), "report.Rmd")
file.copy("report.Rmd", tempReport, overwrite = TRUE)
rmarkdown::render(tempReport,
output_file = file,
params = list(
x_column = input$xcol,
y_column = input$ycol
),
envir = new.env(parent = globalenv())
)
}
)
}
shinyApp(ui, server)
#>
#> Listening on http://127.0.0.1:5776
#> Warning: `aes_string()` was deprecated in ggplot2 3.0.0.
#> ℹ Please use tidy evaluation ideoms with `aes()`