resolução - gráfico de barras

<canvas width="600" heigth="400"></canvas>
<script>
    var tela = document.querySelector("canvas");
    var pincel = tela.getContext("2d");
    var serie2015 = [50, 25, 20, 5];
    var serie2016 = [65, 20, 13, 2];
    var cores = ["blue", "green", "yellow", "red"];

    function desenhaBarra(x, y, serie, cores, texto) {
            pincel.font = "20px Georgia";
            pincel.fillStyle = "black";
            pincel.fillText(texto, x, y - 20);
        for (var i = 0; i < serie.length; i++) {
            pincel.fillStyle = cores[i];
            pincel.fillRect(x, y, 50, serie[i]);
            pincel.fillStroke = "black";
            pincel.strokeRect(x, y, 50, serie[i]);
            y = y + serie[i];
        }
    }


    desenhaBarra(50, 50, serie2015, cores, "2015");
    desenhaBarra(150, 50, serie2016, cores, '2016');
</script>