title: Resetting Input field to null after clicking button in R Shiny
body: <p>I am building an application in which users can enter data values for table by column. Once ADD button is clicked the entered values would be appended by column to the existing one. e.g.
  if col1, 2, 3 are entered and ADD is clicked we have in the display </p>
  
  <pre><code>col1
     2
     3
  </code></pre>
  
  <p>and if col2, 4, 7 are entered and ADD clicked we have have the display</p>
  
  <pre><code>col1 col2
     2    4
     3    7
  </code></pre>
  
  <p>etc.</p>
  
  <p>I would like it such that when the add button is clicked, the input fields are cleared to allow for the entry of new column. Please find below codes for the ui and server. The output table also does not display properly, any assistance to solve this problem too would be appreciated.</p>
  
  <pre><code>ui.R
  
  shinyUI(pageWithSidebar(
  headerPanel("My data table"),
  sidebarPanel(h5("Enter input"),
             textInput("colname","Enter Column Name",NA),
             numericInput("x","X",NA),
             numericInput("y","Y",NA),
             br(),
             actionButton("Add","ADD")),
  mainPanel(verbatimTextOutput("out"))
  ))
  </code></pre>
  
  <p>And </p>
  
  <pre><code>server.R
  
  shinyServer(function(input,output){
  
  myTable &lt;- reactive({
  if(input$Add &gt; 0)
    return(isolate({
      colnm &lt;- input$colname
      x &lt;- input$x
      y &lt;-  input$y
      result &lt;- data.frame(rbind(colnm,x,y))
      result
    }))
  })
  
  output$out &lt;- renderTable({
  myTable()
   })
  
  })
  </code></pre>