var track_update = function (div) {

    var board = tnt.board().from(20).to(500).width(950);

    // Axis track
    var axis_track = tnt.board.track()
        .height(0)
        .color("white")
        .display(tnt.board.track.feature.axis()
             .orientation("top")
        );

    // Data track
    var pin_track = tnt.board.track()
        .height(60)
        .color("white")
        .display(tnt.board.track.feature.pin()
            .index(function (d) {
                return d.pos;
            })
            .domain([0.3, 1.2])
            .color("red")
        )
        .data(tnt.board.track.data.sync()
            .retriever (function () {
                return [
                    {
                        pos : 200,
                        val : 0.5,
                        label : "1"
                    },
                    {
                        pos : 355,
                        val : 0.8,
                        label : "2"
                    },
                    {
                        pos : 100,
                        val : 0.3,
                        label : "3"
                    },
                    {
                        pos : 400,
                        val : 1,
                        label : "4"
                    }
                ];
            })
        );


    board
        .add_track([axis_track, pin_track]);

    board(div);

    // Add 1 more track
    var update = d3.select(div)
        .append("button")
        .text("update track")
        .style("margin", "10px")
        .on("click", function () {
            var data = pin_track.data();
            var display = pin_track.display();

            var elems = data.elements();
            elems.shift();
            data.elements(elems);

            display.update.call(pin_track);

        });

    board.start();
};