D3 function for fitting a projection to geodata

fitProjection.js

function fitProjection(projection, data, box, center) {
    // get the bounding box for the data - might be more efficient approaches
    var left = Infinity,
        bottom = -Infinity,
        right = -Infinity,
        top = Infinity;
    // reset projection
    projection
        .scale(1)
        .translate([0, 0]);
    data.features.forEach(function(feature) {
        d3.geo.bounds(feature).forEach(function(coords) {
            coords = projection(coords);
            var x = coords[0],
                y = coords[1];
            if (x < left) left = x;
            if (x > right) right = x;
            if (y > bottom) bottom = y;
            if (y < top) top = y;
        });
    });
    // project the bounding box, find aspect ratio
    function width(bb) {
        return (bb[1][0] - bb[0][0])
    }
    function height(bb) {
        return (bb[1][1] - bb[0][1]);
    }
    function aspect(bb) {
        return width(bb) / height(bb);
    }
    var startbox = [[left, top],  [right, bottom]],
        a1 = aspect(startbox),
        a2 = aspect(box),
        widthDetermined = a1 > a2,
        scale = widthDetermined ?
            // scale determined by width
            width(box) / width(startbox) :
            // scale determined by height
            height(box) / height(startbox),
        // set x translation
        transX = box[0][0] - startbox[0][0] * scale,
        // set y translation
        transY = box[0][1] - startbox[0][1] * scale;
        console.log(startbox);
    // center if requested
    if (center) {
        if (widthDetermined) {
            transY = transY - (transY + startbox[1][1] * scale - box[1][1])/2;
        } else {
            transX = transX - (transX + startbox[1][0] * scale - box[1][0])/2;
        }
    }
    return projection.scale(scale).translate([transX, transY])
}

Note: at the moment, this only works for Mercator projections.

dude, this saved my life... thanks!

Does this maintain the aspect ratio ?