title: DT in Shiny and R: Custom number formatting
body: <p>I have a shiny-app that displays a datatable using the <code>DT</code>-package. What I want is to be able to format columns in a custom way. For example I want a currency value to be displayed like this: 1,234.50€ instead of the <code>DT</code>-way, which displays it like this $1,234.5 (notice the change in the symbol, the position of the currency-symbol as well as the numbers after the decimal-point).</p>
  
  <p>An MWE looks like this:</p>
  
  <pre><code>library(shiny)
  library(DT)
  
  shinyApp(
    # UI
    ui = fluidPage(DT::dataTableOutput('tbl')),
  
    # SERVER
    server = function(input, output) {
      dat &lt;- data.frame(cur = 1234.5, # supposed to be displayed as: 1,234.50€ | Bad! 
                                           # displayed as $1,234.5
                        perc = 0.123456, # 12.34% | Good!
                        num = 1000) # 1,000 | Bad! displayed as 1000
  
      # render DT
      output$tbl = DT::renderDataTable(
        datatable(dat) %&gt;%
          formatCurrency(c('cur'), "$") %&gt;%
          formatPercentage('perc', 2) %&gt;%
          formatRound('num', digits = 0)
      )
    }
  )
  </code></pre>
  
  <p>It does a fairly good job, however, when changing the currency-symbol to <code>€</code>, the symbol disappears. When inserting another character like "E", the character is still displayed at the beginning not at the end. Furthermore, the numeric value does not get a "big-mark".</p>
  
  <p>Any ideas?</p>