You can programmatically zoom into the required time range using the Axis.setExtremes method. In your case you may want to do it on load

Here is how you would do it, if you want to zoom into the 1st 15 days of the given data, you can easily modify to zoom into last 15 days.

function zoomTo15Points(chart){
    var points=chart.series[0].points;
    if(points.length<15)   return;
    var min=points[0].x;    
    var max=points[14].x;
    // If you wish to zoom to 15 days and not 15 points, you can modify max as
    // var max=min + 1000*60*60*24*14

If you do not want to let the user zoom out, you can disable the last line, but you also will have to disable zooming, else the button would appear if user zooms inside the 15 days.

Highchart Zoom on Load @ jsFiddle


You can try dataGrouping feature of highStock

var dataGrouping = {
    groupPixelWidth: 40,
    units: [[
        [1, 2, 3,4,5,6]

Highcharts would make sure all your columns are at least the specified width (40), if the number of coulmns is large, such that it's not possible to have that width, it will group data using the units, so it will group data of 1 day into 1 column or 2 days into 1 column and so on. Not sure if you really want exactly 15 plots, but I think you concern was to avoid crowding of data, this does exactly that, but the number of columns will vary based on the width you specify, the width of the plotArea and allowed units and its multiples. Tweak the values as per your data and width of your chart. jsFiddle

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