Dynamic number of sliders in Shiny

Question

I am trying to create an application to do exploratory analysis of simulation results datasets that are always in the same (csv) format: first column with run number, several columns that contain the input parameters, one column with the timestep and then several columns that contain the values of interest. The number of input parameters and output values change but the column names that separate these sections are always the same.

Typical data looks like:

[run number],capital,weekly,[step],report1
1,10000,100,0,0
1,10000,100,1,2
1,10000,100,2,3
1,10000,100,3,3

I want the user to be able to select a subset of simulation runs to analyse, using sliders over the input parameters. This means that I need to create the appropriate number of sliders, one for each parameter input.

I have it reading the file and extracting the variable names, and the variables get listed properly. I also have some code working to get a single chooser with all the variables I want (inVarsChooser in code below), so the variable name construction is all correct. But I can't make it create multiple sliders (restrictRuns in code below).

ui code is:

library(shiny)

shinyUI(navbarPage("Test",

  # Choose dataset and display variables
  tabPanel("Input Data",
           sidebarLayout(

             sidebarPanel(
               uiOutput("restrictRuns"),
               br(),
               htmlOutput("inVarsChooser")
             ),

             mainPanel(
               fileInput(inputId = "bsFilename",
                         label = "Load file (table format)",
                         accept=c('text/csv', 'text/comma-separated-values,text/plain',
                                  '.csv'),
                         width = "800px"),

               column(width = 6,
                      h4("Simulation parameters"),
                      htmlOutput("inVarsDisplay")
                      ),

               column(width = 6,
                      h4("Simulation reporters"),
                      htmlOutput("outVarsDisplay")
               )
             )
           )
  )

))

server code is:

library(shiny)

shinyServer(function(input, output, session) {

  bsData <- reactive({
    infile <- input$bsFilename
    if (is.null(infile)){
      return(NULL)      
    }
    read.csv(infile$datapath, stringsAsFactors = TRUE)
  })

  inVars <- reactive({
    df <- bsData()
    if (is.null(df)) return(NULL)
    bsVarnames <- names(df)
    inVars <- bsVarnames[(which(bsVarnames=="X.run.number.")+1):(which(bsVarnames=="X.step.")-1)]
  })

  outVars <- reactive({
    df <- bsData()
    if (is.null(df)) return(NULL)
    bsVarnames <- names(df)
    outVars <- bsVarnames[(which(bsVarnames=="X.step.")+1):length(bsVarnames)]
  })

  output$restrictRuns <- renderUI({
    for (ii in 1:length(inVars())) {
      sliderInput(inputId = paste("range", inVars()[ii], sep=""),
                  label = inVars()[ii],
                  min = 1, max = 1000, value = c(200,500))
    }
  })

  output$inVarsDisplay <- renderUI({
    HTML(paste(inVars(), collapse = '<br/>'))
  })

  output$outVarsDisplay <- renderUI({
    HTML(paste(outVars(), collapse = '<br/>'))
  })

  output$inVarsChooser <- renderUI({
    selectInput("dependent","Select ONE variable as dependent variable from:", inVars())
  })

})

Answer 1

If you want to add sliders for all variables, no matter which one you select in restrictRuns, add this to server.R:

output$sliders <- renderUI({
  pvars <- inVars()
  lapply(seq(pvars), function(i) {
    sliderInput(inputId = paste0("range", pvars[i]),
                label = pvars[i],
                min = 1, max = 1000, value = c(200, 500))
  })

})

and this to ui.R in your sidebarPanel(...):

uiOutput("sliders")

Sidenote:

If you replace:

bsData <- reactive({
  infile <- input$bsFilename
  if (is.null(infile)){
    return(NULL)      
  }
  read.csv(infile$datapath, stringsAsFactors = TRUE)
})

With:

bsData <- reactive({
  validate(
    need(input$bsFilename, "Input a valid filepath.")
  )
  infile <- input$bsFilename
  read.csv(infile$datapath, stringsAsFactors = TRUE)
})

You can get rid of all of the if (is.null(...)) return(NULL)