Can I zoom the map to the extent of a GeoJSON layer?

[palewire]

So, i've created my map

    var po = org.polymaps;
    
    map = po.map()
        .container(document.getElementById("map-canvas").appendChild(po.svg("svg")))
        .zoomRange([1, 6])
        .zoom(4)
        .add(po.interact());
    map.add(po.image().url("http://s3.amazonaws.com/com.modestmaps.bluemarble/{Z}-r{Y}-c{X}.jpg"));

And I've added a JSON layer:

    data = po.geoJson().url("/json/?slug=foo").tile(false);
    map.add(data);

How can I get the map to zoom to the extent of that layer?

[RandomEtc]

I'm not sure if any internal code already calculates the extent of the layer, so you probably need to loop over the features and calculate that yourself.

Once you have the min and max lat/lon of your features you can call map.extent(newExtent) to change the visible area. http://polymaps.org/docs/map.html#extent

[palewire]

Thanks. I think I got it by adding a load function my json that links to:

Array.max = function( array ){
    return Math.max.apply( Math, array );
};
Array.min = function( array ){
    return Math.min.apply( Math, array );
};

function load(e) {
  var x = Array();
  var y = Array();
  for (var i = 0; i < e.features.length; i++) {
    var feature = e.features[i];
    var coords = feature.data.geometry.coordinates;
    var polygons = $.map(coords, function(a){return a});
    var points = $.map(polygons, function(a){return a});
    $.map(points, function(a){
        if(!isNaN(a[0])){x.push(a[0])}; 
        if(!isNaN(a[1])){y.push(a[1])};
    });
  }
  xMax = Array.max(x);
  xMin = Array.min(x);
  yMax = Array.max(y);
  yMin = Array.min(y);
  map.extent([{lon:xMin,lat:yMin},{lon:xMax,lat:yMax}])
}

[drewda]

Just for future reference here's a relevant bit of code: https://github.com/mbostock/polymaps/blob/master/examples/bounds/bounds.js