Shiny allow users to choose which plot outputs to display - r

Question

I have a shiny app and my server function looks like this:
shinyServer(function(input, output, session) {
filedata <- reactive({
infile <- input$file1
if (is.null(infile)) {
return(NULL)
}
myDF <- fread(infile$datapath)
return(myDF)
# Return the requested graph
graphInput <- reactive({
switch(input$graph,
"Plot1" = plot1,
"Plot2" = plot2)
})
output$selected_graph <- renderPlot({
paste(input$graph)
})
output$plot1 <- renderPlot({
#fill in code to create a plot1
})
output$plot2 <- renderPlot({
#fill in code to create plot2
})
The UI function looks like this:
shinyUI(pageWithSidebar(
headerPanel("CSV Viewer"),
sidebarPanel(
fileInput('file1', 'Choose CSV File',
accept=c('text/csv', 'text/comma-separated-values,text/plain', '.csv')),
selectInput("graph", "Choose a graph to view:",
choices = c("Plot1", "Plot2"))
submitButton("Update View")
),#end of sidebar panel
mainPanel(
tabsetPanel(
tabPanel("Graph Viewer", plotOutput("selected_graph"))
)
I can't make the selected plot display on the screen. When I make a selection from the drop-down menu and click the "Update View" button the app does not display the plot. It does not display an error message. It displays nothing at all.
How can I fix this?

Answer 1

As mentioned in the comments, it's difficult to ensure that any answer will work, given the incomplete example in your question. Based on the skeleton server provided, however, this pattern for selecting a graph should work:
shinyServer(function(input, output, session) {
filedata <- reactive({
# Haven't tested that this will read in data correctly;
# assuming it does
infile <- input$file1
if (is.null(infile)) {
return(NULL)
}
myDF <- fread(infile$datapath)
return(myDF)
})
plot1 <- reactive({
# this should be a complete plot image,
# e.g. ggplot(data, aes(x=x, y=y)) + geom_line()
})
plot2 <- reactive({
# this should be a complete plot image,
# e.g. ggplot(data, aes(x=x, y=y)) + geom_line()
})
# Return the requested graph
graphInput <- reactive({
switch(input$graph,
"Plot1" = plot1(),
"Plot2" = plot2()
)
})
output$selected_graph <- renderPlot({
graphInput()
})
}
What changed:
plot1 and plot2 are reactive functions (and not outputs) that can be returned from the graphInput reactive function
graphInput returns the value (i.e. plot) of either plot1 or plot2 into output$selected_graph