R shiny: how to create a list in server.r whose elements are strings indexed by a number n?

Question

I need a line in my server.r code of this type (basically in the server I would arrange all inputs from ui.r in a list):

x<- list(input$field1,input$field2,input$field3, etc... until n=100)
x<- x[!= is.null(x)]
h4(x) 

The code is used inside a renderUI({}). When I write it manually, it works fine. But surely there must be a way to use cat and paste (or other functions) to write it more concisely.

Using the following would not work and I don't get why:

x <- cat(paste("input$field", 1:100,",", sep = ""))
list(x)

Any help/advice would be highly appreciated

ps: I need this because my inputs are generated depending on a button, and so it may be that fields with large Id's such as field99 are not created and I need to test which ones have been created.

Cheers

Answer 1

To get all the input variables as a list, try:

x <- reactiveValuesToList(input)

or,

x <- lapply(1:3, function(z) input[[paste0("field", z)]])

Simple demo: Sum up three user-provided reactive inputs as a list

server.R (EDITED to use second method)

library(shiny)

shinyServer(function(input, output) { 
  output$restable <- renderTable({
    mylist <- lapply(1:3, function(z) input[[paste0("slide", z)]])
    data.frame(Names=c("Slider 1", "Slider 2", "Slider 3", "Sum"),
               Values=c(do.call("c", mylist), do.call("sum", mylist)))
#Values=c(do.call("c", reactiveValuesToList(input)), do.call("sum", reactiveValuesToList(input))))
  })
})

ui.R

library(shiny)

# Define UI for application
shinyUI(pageWithSidebar(

  # Application title
  headerPanel("Sliders should sum to 100!"),

  # Sidebar with 3 slider inputs
  sidebarPanel(
   sliderInput("slide1", "Slider 1: ", min = 0, max = 100, value=40, step=1),
   sliderInput("slide2", "Slider 2: ", min = 0, max = 100, value = 30, step=1),
   sliderInput("slide3", "Slider 3: ", min = 0, max = 100, value = 30, step=1)
  ),

  # Create table output
  mainPanel(
    tableOutput("restable")
  )
))