Custom renderPlot to pdf

Hi, I would like to send a custom plot (not using ggplot2) to a pdf file but cannot work out how to get the contents of renderPlot to the pdf. Below is an example of what I am trying to do. Any ideas on how to do this?
Thanks!

library(shiny)
library(grid)
library(gridExtra)
library(devtools)

ui <- fluidPage(
titlePanel("Old Faithful Geyser Data"),

sidebarLayout(
    sidebarPanel(
        sliderInput("bins",
                    "Number of bins:",
                    min = 1,
                    max = 30,
                    value = 10)
    ),

    mainPanel(
        textOutput("plotTitle"),
       plotOutput("distPlot")
    )
), 
downloadButton('export', "Download pdf")

)

server <- function(input, output) {

plotFunc<-reactive({
    x    <- faithful[, 2]
    bins <- seq(min(x), max(x), length.out = input$bins + 1)
    
    hist(x, breaks = bins, col = 'darkgray', border = 'white')
})

text1<-reactive({
    (paste("The user selected ", input$bins)  )
})

output$plotTitle <- renderText({
    text1()
})

output$distPlot <- renderPlot({
    plotFunc()
})

plotPDF<-reactive({
    grid.grabExpr(print((plotFunc())))
})

output$export = downloadHandler(
    filename = function() {"Plot output.pdf"},
    content = function(file) {
        pdf(file, paper = "default")
        grid.text("This is some initial text",  x=0.5, y=.9, gp=gpar(fontsize=18), check=TRUE)
        grid::grid.newpage()
        grid.text(text1())
        grid.arrange(plotPDF()) #I get stuck here#
        grid::grid.newpage()
        grid.text("This is some final text",  x=0.5, y=.9, gp=gpar(fontsize=18), check=TRUE)
        dev.off()
    }
) 

}

shinyApp(ui = ui, server = server)

Hi,

Welcome to the RStudio community!

You need to explicitly call the plot() function if you want to save an image. That's all you need to do:

output$export = downloadHandler(
    filename = function() {"Plot output.pdf"},
    content = function(file) {
        pdf(file, paper = "default")
        grid.text("This is some initial text",  x=0.5, y=.9, gp=gpar(fontsize=18), check=TRUE)
        grid::grid.newpage()
        grid.text(text1())

        plot(plotFunc()) #this is all you need

        grid::grid.newpage()
        grid.text("This is some final text",  x=0.5, y=.9, gp=gpar(fontsize=18), check=TRUE)
        dev.off()
    }
) 

Hope this helps,
PJ

Hi,

You just use whatever plotting function is used to normally plot the image/graph. Could you give an example?

PJ

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Thanks, that is helpful. Is there is a similar function to plot() that can be used if plotFunc() renders an image instead of a plot?