Object not found error using eventReactive

Question

I have this simple Shiny app in which I want the user to choose among four dataframes -- namely df1, df2, df3 and df4 -- the one than will be displayed using DT:dataTableOutput. The problem is I get this error:

Error in dots_list(...) : object 'df_opt' not found

And I do not know why. I thought the error messages was firing because of something related to the input$df_opt argument I previously had in eventReactive, but then I removed it by adding a button input. Nevertheless, I keep getting the same error message

Does anyone understand why I'm getting this message?

This is a reproducible example of my app:

library(shiny)
library(DT)

 choices_df <- c("opt1", "opt2", "opt3", "opt4")

ui <- fluidPage(
        sidebarLayout(
            sidebarPanel(
                radioButtons(
                    inputId = df_opt,
                    label = "Choose a database",
                    choices = df_choices,
                    selected = choices_df[1] ),
                actionButton(
                  inputId = df_button,
                  label   = "")
                ),
                        mainPanel(
                        DT::dataTableOutput("base_p1")
                          )
            ))


server <- function(input, output) {

  df_selected <- eventReactive(
    input$df_button, { 

      if( input$df_opt == choices_df[1] ){
        df1
      }
      if( input$df_opt == choices_df[2] ){
        df2
      }
      if( input$df_opt == choices_df[3] ){
        df3
      }
      if( input$df_opt == choices_df[4] ){
        df4
      }

     })

  output$base_p1 <- DT::renderDataTable( df_selected(), filter = "top")
}

shinyApp(ui = ui, server = server)

Maybe replace your df_opt in quotes "df_opt" in inputId ? — Ravi
– Ravi, Commented Dec 19, 2019 at 12:02
Indeed! My mistake was so simple that I did not even consider it. Thank you very much! — Pascual Esteban
– Pascual Esteban, Commented Dec 19, 2019 at 17:27

JacobJacox · Accepted Answer · 2019-12-19 12:32:30Z

1

Here is a working version of what you want to do, but with reactiveValues. So basically I find it better to create like an empty holder for reactive variable, then just assign the wanted df to it when user changes input. Code:

library(shiny)

library(DT)

df_choices <- c("opt1", "opt2", "opt3", "opt4")

df1 <- matrix(rnorm(100,10,10),10,10)
df2 <- matrix(rnorm(100,100,10),10,10)
df3 <- matrix(rnorm(100,1099,10),10,10)
df4 <- matrix(rnorm(100,100000,10),10,10)

ui <- fluidPage(
  sidebarLayout(
    sidebarPanel(
      radioButtons(
        inputId = "df_opt",
        label = "Choose a database",
        choices = df_choices,
        selected = choices_df[1] ),
      actionButton(
        inputId = "df_button",
        label   = "click to show")
    ),
    mainPanel(
      DT::dataTableOutput("base_p1")
    )
  ))


server <- function(input, output) {

df <- reactiveValues(df=df1)

  observeEvent(input$df_button,{
    if( input$df_opt == choices_df[1] ){
      df$df <- df1
    }
    if( input$df_opt == choices_df[2] ){
      df$df <-df2
    }
    if( input$df_opt == choices_df[3] ){
      df$df <- df3
    }
    if( input$df_opt == choices_df[4] ){
      df$df <- df4
    }
  })

  output$base_p1 <- DT::renderDataTable( df$df, filter = "top")
}

shinyApp(ui = ui, server = server)

EDIT: And yes, inputID should be strings, so "df_opt" and "df_button".

answered Dec 19, 2019 at 12:32

JacobJacox

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2 Comments

Pascual Esteban Over a year ago

Thank you for your answer! Do you prefer the reactiveValues way because you find it more straight or because of some performance consideration?

JacobJacox Over a year ago

That depends on your code, if your event is expensive then it is better to calculate once and save it. I usually do operations on the reactive variable, so it is too expensive to calculate it every time. Please accept the answer by clicking on green tick below upvote buttons. :)

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