server.R undefined columns?

Question

I'm trying to create a R Shiny app and have encountered the error:

Error in `[.data.frame`(dataset.temp, , input$col) : 
  undefined columns selected

I'm not sure what's causing this, hopefully someone could help me figure it out. Here's a sample code:

ui.R

shinyUI(fluidPage(
  titlePanel("Data"),
  sidebarLayout(
    sidebarPanel(
      textInput("from","Missing",
                value="Enter characters"),
      textInput("to","Missing",
                value="Enter characters"),
      selectInput("col","Select Column",
                  choices = c(1:6),
                  selected=1)),
    mainPanel(
      tableOutput('contents')
    )
  )
))

server.R

library(DT)
file <- read.csv("file.csv")
shinyServer(function(input, output) {
dataset.temp <- file
output$contents <- renderTable({
dataset.temp[,input$col] <- gsub(input$from,input$to,dataset.temp[,input$col])
    dataset.temp
  })
})

Any thoughts?

Answer 1

I got a different error from running your code:

Error in `[.data.frame`(dataset.temp, , input$col) : 
  undefined columns selected

The cause (at least for my error) is that input$col is a string and you're treating it as an integer. There are two possible fixes:

1. Change your selectInput to a numericInput, which means that now input$col returns an integer, or
2. Manually convert input$col to an integer with col <- as.integer(input$col)

Using the second approach, here's the complete code.

runApp(shinyApp(
  ui = fluidPage(
    titlePanel("Data"),
    sidebarLayout(
      sidebarPanel(
        textInput("from","Missing",
                  value="Enter characters"),
        textInput("to","Missing",
                  value="Enter characters"),
        selectInput("col","Select Column",
                    choices = c(1:6),
                    selected=1)),
      mainPanel(
        tableOutput('contents')
      )
    )
  ),
  server = function(input, output) {
    dataset.temp <- file
    output$contents <- renderTable({
        col <- as.integer(input$col)
        dataset.temp[,col] <- gsub(input$from, input$to,dataset.temp[,col])
      dataset.temp
    })
  }

))

I don't know what file you're using so I just used my own csv file and it works