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 from the UI. The input from the UI is dynamic as well.

Here is my UI.R:

shinyUI(pageWithSidebar(
  headerPanel("Dynamic number of plots"),
  sidebarPanel(
    selectInput("Desk", "Desk:" ,  c("A","B")),
   uiOutput("choose_Product"),
uiOutput("choose_File1"),
uiOutput("choose_Term1"),
sliderInput("n", "Number of plots", value=1, min=1, max=5)
  ),

  mainPanel(
    # This is the dynamic UI for the plots
    h3("Heading 1"),
    uiOutput("plots"),
   h3("Heading 2")
  )
))

Here is my Server.R:

shinyServer(function(input, output) {

  output$choose_Product <- renderUI({
    selectInput("Product", "Product:", as.list( c("Product1","Product2","Product3")))
  })

  output$choose_File1 <- renderUI({
selectInput("File1", "File1:", as.list(c("File1","File2","File3")))
  })

# Insert the right number of plot output objects into the web page

  output$plots <- renderUI({
      plot_output_list <- lapply(1:input$n, function(i) {
        plotname <- paste("plot", i, sep="")
        plotOutput(plotname, height = 280, width = 250)
      })

      # Convert the list to a tagList - this is necessary for the list of items
      # to display properly.
      do.call(tagList, plot_output_list)
  })##End outputplots

  PrintPlots<- reactive({
## I need max_plots to be set as the length of the Vector returns from getAugmentedTerms()
max_plots<-length(getAugmentedTerms(input$Desk, input$Product, input$File1))

# Call renderPlot for each one. Plots are only actually generated when they
# are visible on the web page.

for (i in 1:max_plots) {
  # 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 = "") )
        })
      })
    }##### End FoR Loop
  })# END OF PRINT PLOTS
})# END OF ENERYTHING

Here is my global.R:

getAugmentedTerms<-function(desk, product, file)
{
   # this function takes 3 inputs from the UI and returns a vector
   # for simplicity I am just returning a 2 element vector
   d<-c(1,2)
   return d
}

Here is code to run it:

library(shiny)
runApp("C:/Users/user/Desktop/R Projects/TestDynamicPlot")

When you run this you can see space is created like there are being plots output but the output is blank. Any ideas? Thank you!

The input object is undefined outside the shiny server function. And in the example max_plots is hard coded, input$n for the loop creating the plot ouputs isn't — Julien Navarre
@user3022875 Post your comments as a separate answer or edit your question, do not edit others' answers. — vortexwolf

Julien Navarre Julien Navarre · Accepted Answer · 2014-04-03T15:17:13

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) {
       ...

R Shiny loop to display multiple plots

1 Answers