[Chartjs]-Chart from Database

php:

$dates=array();
$pcrs=array();
while ($row = mysql_fetch_array($result, MYSQL_ASSOC)) {
    $dates[] = $row['Date'];
    $pcrs[] = $row['Pcr']; 
}
$data = ["dates"=>$dates,"pcrs"=>$pcrs];
echo json_encode($data);

js:

 $(document).ready(function(){ 
            $.ajax({
                type:'GET',
                url:'data.php',

                success:function(data){
                    var Datos = {
                            labels : data.dates,
                            datasets : [
                                {

                                    fillColor : 'rgba(255,0,0,0.1)', 
                                    strokeColor :'rgba(255,0,0,100)',
                                    pointColor : 'rgba(255,0,0,100)',
                                    pointStrokeColor:"#e32636",
                                    pointHighlightFill:"#bbf",
                                    pointHighlightStroke:"rgba(255,0,0,255)",

                                    data : data.pcrs
                                } 
                            ]
                    }

                    var contexto = document.getElementById('grafico').getContext('2d');
                    var chrt = new Chart(contexto).Line(Datos, { responsive : true });
                }
            });
            return false;
        }
        )