CODEWITHSUNDEEP
rshiny
giyenga1
giyenga1

Reputation: 13

Dependent Dropdowns on Shiny

I am writing a shiny script where a file is uploaded, a dropdown appears with the column names from that file, and then a second dropdown appears with the unique values from the column in the file selected in the first dropdown. I was able to create the first dropdown, but am having trouble with the second dropdown. Here is my code thus far: 

ui <- fluidPage(

titlePanel("File Upload Test"),

sidebarLayout(
  sidebarPanel(
     fileInput("file1", "Choose csv file",
               multiple = T,
               accept = c(".csv")),

uiOutput("y_input"),
uiOutput("target_input")),

mainPanel(
plotOutput("contents"))))

server <- function(input, output, session) {

inFile <- reactive({
if (is.null(input$file1)) {
  return(NULL)
} else {
  input$file1}
})

myData <- reactive({
if (is.null(inFile())) {
  return(NULL)
} else {
  read.csv(inFile()$datapath)}
})

output$y_input <- renderUI({
if (is.null(inFile())) {
  return(NULL)
} else {
selectInput("y_output", "Select Y Variable", names(myData()))}
})

output$target_input <- renderUI({
if (is.null(input$y_input)) {
  return(NULL)
} else {
  selectInput("target_output", "Select Target Group", 
              myData( [,input$y_output])}
})
}

Any help here is appreciated! This is my first post on stack overflow, so if there are any formatting or clarity things in this post I can/should fix please let me know! Thanks!

Upvotes: 1

Views: 3261

Answers (1)

GyD
GyD

Reputation: 4072

First of all some tips to improve your code:

  1. Use req

req(name_of_input) is shorthand for if(is.null(name_of_input)) return NULL. It will save you a few strokes while providing better readability.

  1. Your reactive called inFile is unnecessary

Use input$file1$datapath instead. Again this is more concise while having better performance as well.

myData <- reactive({
  req(input$file1)
  read.csv(input$file1$datapath)
})

And finally the problem:

Your reference to myData is wrong. The subsetting part of [,input$y_output] should be outside of the parentheses, like this: myData()[,input$y_output]. Keep in mind that even though reactives look like functions they don't take any arguments.

Full server.R:

server <- function(input, output, session) {
  myData <- reactive({
    req(input$file1)
    read.csv(input$file1$datapath)
  })

  output$y_input <- renderUI({
    req(input$file1)
    selectInput("y_output", "Select Y Variable", names(myData()))
  })

  output$target_input <- renderUI({
    req(input$file1)
    selectInput("target_output", "Select Target Group", 
                myData()[,input$y_output]
    )
  })
}

ps: Welcome to stackoverflow! :)

Upvotes: 5

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