object of type 'closure' is not subsettable in shiny. Working on a simple RGL plotting function

Question

I was coding in shiny with the rgl and shinyRGL package, trying to plot a 3D line plot by having the users insert a csv file of a specific format. But the object type closure error keeps showing up. It seems like because it can't find the function plot3d, or I may be wrong.

Here's the code:

UI

library(shiny)
library(rgl)
library(shinyRGL)

# Define UI for application that draws a histogram
shinyUI(fluidPage(
  titlePanel("title panel"),

  sidebarLayout(
    sidebarPanel(
      helpText("Please select a CSV file with the correct format."),
      tags$hr(),
      fileInput("file","Choose file to upload",accept = c(
        'text/csv',
        'text/comma-separated-values',
        'text/tab-separated-values',
        'text/plain',
        '.csv',
        '.tsv',
        label = h3("File input"))
    ),
    tags$hr(),
    checkboxInput('header', 'Header', TRUE),

    actionButton("graph","PLOT!")
    ),


mainPanel(textOutput("text1"),
          webGLOutput("Aplot")))
)
)

Server

library(shiny)
library(rgl)
library(shinyRGL)

options(shiny.maxRequestSize = 9*1024^2)
shinyServer(
  function(input, output) {


    output$text1 <- renderText({
    paste("You have selected", input$select)
  })
    output$"Aplot" <- renderWebGL({
      inFile <- reactive(input$file)
      theFrames <- eventReactive(input$graph,read.csv(inFile$datapath,
header = input$header))
plot3d(theFrames[[4]],theFrames[[5]],theFrames[[6]],xlab="x",ylab="y",zlab 
= "z", type = "l", col = ifelse(theFrames[[20]]>0.76,"red","blue"))
   })
})

Error

Warning: package hinyRGL?was built under R version 3.3.1 Warning: Error in [[: object of type 'closure' is not subsettable Stack trace (innermost first): 70: plot3d 69: func [C:\Users\Ian\workspace\Copy of Leap SDK/Test\App_1/server.R#19] 68: output$Aplot 1: runApp

It's not that it can't find the function, it's that somewhere in those functions you're trying to subset a closure (a function), which obviously doesn't work. Try swapping out subsetted dynamic terms with static placeholders (anything that you know will let the function run) so you can figure out which term is causing the issue. — alistaire
@alistaire It seems like the issue is within my XYZ parameter "theFrames[[...]]". But I don't know what's causing it or how to fix it. — I AN Lee
@alistaire It is just the data frame which stores the csv file. The plot3d function access it for the XYZ coordinates for the plot. — I AN Lee
I suspect eventReactive is somehow not returning what you expect. — alistaire

K. Rohde K. Rohde · Accepted Answer · 2016-07-14T07:28:12

Remember this error message, since it's very typical for shiny applications.

It almost always means, that you had a reactive value, but didn't use it with parentheses.

Concerning your code, I spotted this mistake here:

inFile <- reactive(input$file)
theFrames <- eventReactive(input$graph,read.csv(inFile$datapath,
    header = input$header)) 

plot3d(theFrames[[4]],theFrames[[5]],theFrames[[6]],xlab="x",ylab="y",zlab 
    = "z", type = "l", col = ifelse(theFrames[[20]]>0.76,"red","blue"))

You use inFile like a normal variable, but it isn't. It's a reactive value and thus has to be called with inFile(). The same goes for theFrames, which you called with theFrames[[i]], but should be called with theFrames()[[i]].

So the correct version would be

inFile <- reactive(input$file)
theFrames <- eventReactive(input$graph,read.csv(inFile()$datapath,
    header = input$header)) 

plot3d(theFrames()[[4]],theFrames()[[5]],theFrames()[[6]],xlab="x",ylab="y",zlab 
    = "z", type = "l", col = ifelse(theFrames()[[20]]>0.76,"red","blue"))

Maybe some additional info about the error message: Shiny evaluates the variables only when they are needed, so the reactive theFrames, containing the error, is executed from inside the plot3d function. That is why the error message tells you something about the error being in plot3d, even if the error lies somewhere else.

object of type 'closure' is not subsettable in shiny. Working on a simple RGL plotting function

2 Answers