Producing dynamic/multiple input boxes to collect data depending on user selection in Shiny R

Question

I am trying to build an app in Shiny that (1) asks user for number of Assets in his/her portfolio. Depending on the numeric entry, (2) the user is presented with one numeric bo

Answer 1

ui.R

library(shiny)

shinyUI(pageWithSidebar (

  headerPanel( "Portfolio Returns"),

  sidebarPanel(
    numericInput("assets", label = "Enter Number of Assets in Portfolio", value="1"),
    uiOutput("tickers")
  ),
  mainPanel()
)) 

server.R
-Note that to pass multiple items in the renderUI() function you have to group them into a list, and here lapply() is creating a list of lists.

library(shiny)

shinyServer( function(input, output, session) {

  output$tickers <- renderUI({
    numAssets <- as.integer(input$assets)

    lapply(1:numAssets, function(i) {
      list(tags$p(tags$u(h4(paste0("Asset ", i)))),
           textInput(paste0("ticker", i), label = "Ticker Name", value = "Enter ticker..."),
           numericInput(paste0("weight", i), label = "Weight of Asset", value=0))  
    })
  })
})