title: how customize the dataTableOutput in shiny app
body: <p>I want to see only three records in each page of my dataTableOutput. I have set page length to (<code>pageLength = 3</code>) but it does not show 3 rows in my table. 
  The code is as following:</p>
  
  <blockquote>
    <p>server.r :</p>
  </blockquote>
  
  <pre><code># display table
    output$responses &lt;- DT::renderDataTable({
      (options = list(pageLength = 3))
      #update after submit is clicked
      input$submit
      #update after delete is clicked
      input$delete
      ReadData()
    }
  </code></pre>
  
  <blockquote>
    <p>ui.r :</p>
  </blockquote>
  
  <pre><code> box(
        title = "KPIs", status = "primary", solidHeader = TRUE,
        collapsible = TRUE,
       DT::dataTableOutput("responses"), tags$hr()
  
      ))
  </code></pre>