code: function updateExpression() {
    var input = $('.expression');
    var expression = input.val();
    $('.plot').hide();
  
    if (!expression) {
      // No expression specified. Don't plot.
      input.css('background-color', '#fff');
      return;
    }
  
    try {
      var plotFunction = compileExpression(expression, additionalFunctions); // <-- Filtrex!
      input.css('background-color', '#dfd');
    } catch (e) {
      // Failed to parse expression. Don't plot.
      input.css('background-color', '#fdd');
      return;
    }
  
    render(plotFunction);
  }
docs: When user entered expression changes, attempt to parse it
  and colorize rows based on expression.