title: Extract filters from R Shiny Datatable
body: <p>I have a <a href="https://rstudio.github.io/DT/" rel="nofollow noreferrer">DT data table</a> in R Shiny and I have enabled column filtering by setting <code>filter="top"</code> within <code>renderDT()</code>. I now want to extract the user-applied filters so I can save them in variables server-side and reapply them when -- for instance -- a database is updated, requiring an update of the table.</p>
  
  <p>Here's a MWE using Shiny Dashboard:</p>
  
  <pre><code>library(shiny)           #  Shiny web app
  library(shinydashboard)  #  Dashboard framework for Shiny
  library(plotly)          #  Plotly interactive plots
  library(DT)
  
  ui &lt;- dashboardPage(
    dashboardHeader(),
    dashboardSidebar(),
    dashboardBody(
      fluidRow(column(12, DTOutput("table")))
    )
  )
  
  server &lt;- function(input, output, session) {
    fileData &lt;- reactiveFileReader(1000, session, 'test.csv', read.csv)
    output$table &lt;- renderDT(fileData(), filter = "top")
  }
  
  shinyApp(ui, server)
  </code></pre>
  
  <p>To reiterate, I'd like to save the filters (for instance, a user might select a range of numeric values or a specific factor from one of the filter boxes) as <code>input$</code> variables so I can use them on the server side.</p>