I am trying to display some timelines using D3 stacked chart. I got this errors

Error: attribute x: Expected length, "NaN". Error: attribute width: Expected length, "NaN".

Here is my adapted source code:

$scope.createTimeline = function(callsSource, tag, nameField) {
    var colorScale = d3.scale.ordinal().range(['#008000','#FF0000']).domain(['ok','ko']);
    var chart = d3.timeline()
    .rotateTicks(45)
    .stack()
    .itemHeight(12)
    .itemMargin(2)
    .showTimeAxisTick()
    .tickFormat({format: d3.time.format("%X.%L"), numTicks:15, tickSize: 5})
    .showTimeAxisTickFormat({stroke: "stroke-dasharray", spacing: "4 5"})
    .colors( colorScale )
    .colorProperty('status');

    var svg = d3.select(tag).append("svg").attr("width", 950);
    var listSeg = new Array();
    var calls = callsSource.slice(0);
    calls.reverse();
    for (var i = 0; i < calls.length; i++) {
        var seg = {status:(calls[i].retHttp == "200" ? 'ok' : 'ko'), times: [{label:calls[i][nameField]||"unknown","starting_time": calls[i].startDate||calls[i].endDate, "ending_time": calls[i].endDate||calls[i].startDate}]};
        listSeg.push(seg);
    }
    svg = svg.datum(listSeg).call(chart);
};

The errors i console:

When i inspect my HTML page, i can see that in my svg x and width attributes are NaN

Any help please!