Using a download handler to save ggplot images in shiny - r

Question

I am developing an application in shiny.In shiny, I am rendering a simple plot using the action button. I have included a download button to download the the plot that is now in UI. from my code(plot3)
I tried the below code, to save the image, but I am getting an error
plotInput not found.
Could any one suggest where i am going wrong.
Below is my code for reference.
UI:
ui <- tabItem(tabName = "models2",
fluidPage(
fluidRow(
infoBoxOutput("overview")
),
fluidRow(
actionButton("result1","Generate Result"),
downloadButton('downloadPlot','Download Plot'),
plotOutput("plot3")
)
))
SERVER
server <- function(input,output,session{
output$overview <- renderValueBox({
valueBox(
paste("91"),"Overview",icon=icon("hourglass"),
color="green"
)
})
observeEvent(input$result1,{
output$plot3 <- renderPlot({
ggplot(data=timedata, aes(x=dat1, y=yes, group=3))+
geom_point(shape=1)+
coord_cartesian(xlim=c(dat1_xlowlim,dat1_xhighlim))+
labs(title="Probability",x="Date",y="True probability")
})
})
output$downloadPlot <- downloadHandler(
filename = function(){paste(input$plot3,'.png',sep='')},
content = function(plot3){
ggsave(plot3,plotInput())
}
)
})
Also, to note my shiny and R studio are in R environment.

Answer 1

library(shiny)
library(shinydashboard)
ui <- tabItem(tabName = "models2",
fluidPage(
fluidRow(
infoBoxOutput("overview")
),
fluidRow(
actionButton("result1","Generate Result"),
downloadButton('downloadPlot','Download Plot'),
plotOutput("plot3")
)
))
server <- function(input,output,session){
output$overview <- renderValueBox({
valueBox(
paste("91"),"Overview",icon=icon("hourglass"),
color="green"
)
})
data <- reactiveValues()
observeEvent(input$result1,{
data$plot <- ggplot(data=iris, aes(x=Sepal.Length, y=Sepal.Width))+
geom_point(shape=1)})
output$plot3 <- renderPlot({ data$plot })
output$downloadPlot <- downloadHandler(
filename = function(){paste("input$plot3",'.png',sep='')},
content = function(file){
ggsave(file,plot=data$plot)
}
)
}
shinyApp(ui, server)

Answer 2

#Mikz
I don't have enough reputation to follow your comment. Thus, I create a new anwser but wish to answer your question 'why app closes automatically?'.
I had same issue when I develop shiny app on rstudio-server of my company. My app will close by itself after a while. However, same app run on my local laptop don't have this issue.
After my research, I believe it caused by timeout setting (default is 60 seconds). I also use function ~~Sys.sleep()~~ to test this default time. I found the solution works for me from this blog .
The idea is using WebSocket to trigger app every 50 seconds. In this way, you don't need to ask technique guy to adjust setting on server level.