Warning: Error in [: object of type 'closure' is not subsettable

[Maferdata]

library(shiny)
library(shinydashboard)
library(shiny)
#library(leaflet)
#library(leaflet.extras)

header <- dashboardHeader(
  dropdownMenu(
    type = "messages",
    messageItem(
      from = "Data",
      message = "Learn how to do your Shiny App",
      href = "https://rstudio.github.io/shinydashboard/structure.html#sidebar-menu-items-and-tabs"
    )
  )
)

sidebar <- dashboardSidebar(
  sidebarMenu(
    menuItem("Dashboard", tabName = "dashboard", icon = icon("dashboard")),
    menuItem("Widgets", icon = icon("th"), tabName = "widgets",
             badgeLabel = "new", badgeColor = "green"),
    fileInput("file1", "Choose CSV File",
              multiple = TRUE,
              accept = c("text/csv",
                         "text/comma-separated-values,text/plain",".csv")),
    sliderInput("bins",
                "Number of bins:",
                min = 1,
                max = 10000,
                value = 500), 
    sliderInput("opacity", "Opacity:",
                min = 0, max = 1,
                value = 0.5, step = 0.1)
  )
)
body <- dashboardBody(
  tabItems(
    tabItem(tabName = "dashboard",
            h2("Dashboard tab content")
    ),
    tabItem(tabName = "widgets",
            h2("Widgets tab content")
    )
  ),
      mainPanel(
        plotOutput("distPlot")
      ) #main panel
  ) #body

ui <- dashboardPage(header, sidebar, body)


# Define server logic required to draw a histogram
server <- function(input, output) {
  mydataset <- reactive({
    print("started mydata <- reactive")
    inputfile1 <- input$file1
    if (is.null(inputfile1)) return(NULL)
    df1 = data.frame(read.csv(inputfile1$datapath, as.is=TRUE))
    #VALIDATE DATA
    print("ended mydata <- reactive")
    return(df1)
  })
  observeEvent(input$file1, {
    output$distPlot <- renderPlot({
      # generate bins based on input$bins from ui.R
      x    <- mydataset[,2] 
      bins <- seq(min(x), max(x), length.out = input$bins + 1)
      
      # draw the histogram with the specified number of bins
      hist(x, breaks = bins, col = 'darkgray', border = 'white')
   }) # renderPlot
}) #observeEvent
}#server    
     

# Run the application 
shinyApp(ui = ui, server = server)

[EconomiCurtis]

There's a handy Shiny Debugging guide here,

Shiny debugging and reprex guide

Shiny issues can be challenging to resolve relative to other problems with your code or statistical methods. Shiny apps are often large, complex projects with interacting files. When seeking help from others it is considered polite to: First, do your best to work through RStudio's debugging tools to diagnose your issue on your own. Often those shiny logs and tracebacks are useful to others trying to help out. Second, strive to minimize the effort required to replicate your issue. You can do this with a reproducible example ("reprex"). Shiny Debugging Errors in Shiny code can be difficult to track down. If you don't know where your problem is coming from, you can track it down with some o…

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Your error message, in a shiny app, usually means you are trying to perform an operation you'd usually perform on a data frame on a function (that is, a closure).

I suspect this error is popping up on the line with x <- mydataset[,2] , perhaps after you've loaded that gets returned NULL where mydataset is set up...

---

[Maferdata]

So what you mean is that I am subsetting a closure which is a function? How can i solve this problem?

[Maferdata]

How can i specify that I want an specific column for the histogram? Thank you!

[EconomiCurtis]

Where is this demo app coming from?

The issue is in the part of your code where the file is loaded.

Here's a nice article I'd work through to get familiar with best practices for how to do this,

Shiny - Help users upload files to your app

The req function if your friend.

---

One quick option is to replace your server seciton with something like

# Define server logic required to draw a histogram
server <- function(input, output) {

  observeEvent(input$file1, {
    output$distPlot <- renderPlot({
      
      req(input$file1)
      df1 <- read.csv(input$file1$datapath)
      # generate bins based on input$bins from ui.R
      x    <- df1[,2] 
      bins <- seq(min(x), max(x), length.out = input$bins + 1)
      
      # draw the histogram with the specified number of bins
      hist(x, breaks = bins, col = 'darkgray', border = 'white')
    }) # renderPlot
  }) #observeEvent
}#server    

Note I load the dataset inside where the plot is created.

The tutorial at Redirect has a really nice, quick overview of how to get a shiny app working. It, plus the Help users upload files to your app guide should get you off to the races.

---

Also in the line x <- mydataset[,2], your hist will be built only off the second column/variable in the file you provide.

histograms

Here's a nice guide on making histograms with r

How to Make a Histogram with Basic R | R-bloggers

Also, GGPLOT2: Histograms and frequency polygons

[nwerth]

@Maferdata

mydataset <- reactive({ ... })

observeEvent(input$file1, {
    output$distPlot <- renderPlot({
      # generate bins based on input$bins from ui.R
      x    <- mydataset[,2] 

mydataset is a reactive object, not a data.frame. You need to ask it for its value. Try this:

observeEvent(input$file1, {
    output$distPlot <- renderPlot({
      # generate bins based on input$bins from ui.R
      x    <- mydataset()[,2]