This example belongs to the presentation made to the OSGeo local group in Barcelona Geoinquiets The example is an adaptation from Mike Bostock‘s Symbol Map example
<!DOCTYPE html>
<meta charset="utf-8">
<style>
.states {
fill: #ccc;
stroke: #fff;
}
</style>
<body>
<button type="button" id="change">Change</button>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v0.min.js"></script>
<script>
var width = 960,
height = 500;
var states;
var projection = d3.geo.mercator()
.center([-97,37])
.scale(4000 / 2 / Math.PI)
.translate([width / 2, height / 2]);
var path = d3.geo.path()
.projection(projection);
var svg = d3.select("body").append("svg")
.attr("width", width)
.attr("height", height);
d3.json("/mbostock/raw/4090846/us.json", function(error, us) {
states = svg.append("path")
.attr("class", "states")
.datum(topojson.object(us, us.objects.states))
.attr("d", path);
});
d3.select("#change").on("click", function() {
projection = d3.geo.albers();
path.projection(projection);
states.transition()
.duration(10000)
.attr("d", path);
});
</script>