title: Warning: Error in filter renderDataTable
body: <p>I am trying to create Search Tool in R <a href="/questions/tagged/shiny" class="post-tag" title="show questions tagged &#39;shiny&#39;" rel="tag">shiny</a> as below code
  However, it popped up with error message once run</p>
  
  <pre><code>Warning: Error in filter: object 'Category' not found
    [No stack trace available]
  </code></pre>
  
  <p>I am new with R shiny. Any recommendation would be greatly appreciated
  Thanks heaps</p>
  
  <pre><code>library(shiny)
  library(DT)
  
  # Data frame
  df &lt;- read.csv("Z:/Valuations Risk &amp; Quality/July 2018- Commercial Panel Look up Tool - R/CSV/PanelFirmList.csv", header=TRUE)
  df$Postcode&lt;- as.character(df$Postcode)
  df &lt;- df[,c(4,3,6,9,10,11,12,13,14)]
  
  # Define UI for application that draws a histogram
  ui &lt;- fluidPage(
  
    # Application title
    titlePanel("NAB Panel lookup tool"),
  
    # Postcode textbox 
    sidebarLayout(
      sidebarPanel(
        textInput("postcode",
                  "Postcode"
        ),
        selectInput("category",
                    "Category",
                    choices = unique(df$Category)
        ),
        selectInput("panel",
                    "Panel Type",
                    choices = unique(df$Panel_Type)
        ),
        selectInput("value",
                    "Value Range",
                    choices = unique(df$Value_Range)
        )
      ),
      # Show filtered data frame
      mainPanel(
        DT::dataTableOutput("table")
      )
    )
  )
  
  # Define server logic required to produce table
  server &lt;- function(input, output, session) {
  
      output$table &lt;- DT::renderDataTable({
      df %&gt;% 
        filter ((Postcode == input$postcode) &amp; (Category == input$category) &amp; (Panel_Type == input$panel) &amp; (Value_Range == input$value)) %&gt;% 
        select(c(Region, Valifirm, Email, Phone))
    })
  }
  # Run the application 
  shinyApp(ui = ui, server = server) 
  </code></pre>