I have followed this tutorial in order to use amChart and it worked with no problems , now I am trying to generate a chart with amCharts to show each user and the sign in count but i cant make it work because it not getting the data correctly, what i am missing here ?

how can i show user email and sign_in_count ?

Users_controller.rb

class UsersController < ApplicationController
  load_and_authorize_resource
  def index
    @users = User.all
    respond_to do |format|
     format.html  # index.html.erb
     format.json  { render :json => @users }
    end
  end

  def show
    @user = User.find(params[:id])

  end


  def new
    @user = User.new
  end

  def create
    @user = User.new(params[:user])
    if @user.save
      flash[:notice] = 'A new user created successfully.'
      redirect_to users_path
    else
      flash[:error] = 'An error occurred please try again!'
      redirect_to users_path
    end
  end

  def edit
    @user = User.find(params[:id])
  end

  def update
    @user = User.find(params[:id])
    if @user.update_attributes(params[:user])
      flash[:notice] = 'Profile updated'
      redirect_to users_path
    else
      render 'edit'
    end
  end

  def destroy
    @user = User.find(params[:id])
    if current_user == (@user)
      flash[:error] = "Admin suicide warning: Can't delete yourself."
    else
      @user.destroy
      flash[:notice] = 'User deleted'
      redirect_to users_path
    end
  end

  def checkname
    if User.where('user_name = ?', params[:user]).count == 0
      render :nothing => true, :status => 200
    else
      render :nothing => true, :status => 409
    end
    return
  end

end

Users_helper.rb

module UsersHelper
    def convert_to_amcharts_json(data_array)
        data_array.to_json.gsub(/\"text\"/, "text").html_safe
    end
end

index.html.erb

 <div id="chartdiv" style="width: 100%; height: 400px;"></div>

<script type="text/javascript">
            var chart;

            var chartData = <%= convert_to_amcharts_json(@users) %>;


            AmCharts.ready(function () {
    // SERIAL CHART
    chart = new AmCharts.AmSerialChart();
    chart.dataProvider = chartData;
    chart.categoryField = "email";
    // the following two lines makes chart 3D
    chart.depth3D = 20;
    chart.angle = 30;

    // AXES
    // category
    var categoryAxis = chart.categoryAxis;
    categoryAxis.labelRotation = 90;
    categoryAxis.dashLength = 5;
    categoryAxis.gridPosition = "start";

    // value
    var valueAxis = new AmCharts.ValueAxis();
    valueAxis.title = "Most Active users";
    valueAxis.dashLength = 5;
    chart.addValueAxis(valueAxis);

    // GRAPH            
    var graph = new AmCharts.AmGraph();
    graph.valueField = "sign_in_count";
    graph.colorField = "color";
    graph.balloonText = "<span style='font-size:14px'>[[category]]: <b>[[value]]</b></span>";
    graph.type = "column";
    graph.lineAlpha = 0;
    graph.fillAlphas = 1;
    chart.addGraph(graph);

    // CURSOR
    var chartCursor = new AmCharts.ChartCursor();
    chartCursor.cursorAlpha = 0;
    chartCursor.zoomable = false;
    chartCursor.categoryBalloonEnabled = false;
    chart.addChartCursor(chartCursor);                

    // WRITE
    chart.write("chartdiv");
});
        </script>