R Shiny loop to display multiple plots

Question

Ok I have code that you can run below. I am trying to modify this code:

https://gist.github.com/wch/5436415/

so that max_plots is dynamically set using input

Answer 1

So max_plots is hard coded. When you launch the app, the loop for (i in 1:max_plots ) { (It runs only once) creates 5 (= max_plots) new output elements (output$plot1 output$plot2 ...) which render a plot, but the plots are displayed only when the respectiveplotOutputsexists in the UI. TheplotOutputs are created dynamically in the functionlapply(1:input$n, function(i) {input$n is the value of the slider. 5 plots are created but we only createinput$nplot outputs. That's why this is dynamic even ifmax_plots` is hard coded.

If you want you can replace max_plots by the dynamic parameter but you need to include the loop into and observer. And it will run each time input$n changed.

For example :

observe({
    for (i in 1:input$n) {
        # Need local so that each item gets its own number. Without it, the value
        # of i in the renderPlot() will be the same across all instances, because
        # of when the expression is evaluated.
        local({
          my_i <- i
          plotname <- paste("plot", my_i, sep="")

          output[[plotname]] <- renderPlot({
            plot(1:my_i, 1:my_i,
                 xlim = c(1, max_plots),
                 ylim = c(1, max_plots),
                 main = paste("1:", my_i, ". n is ", input$n, sep = "")
            )
          })
        })
     }
})

I don't know what your function returns but i suppose it can also work if you include it into the server function and inside a reactive function in which you can read input object.

observe({ 
    max_plots<-length(getTerm1UI(input$Desk, input$Product, input$File1))
    for(i in 1:max_plots) {
       ...