<!doctype html>
<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.6/d3.min.js" charset="utf-8"></script>
</head>
<body>
<script>
var dataArray =[20, 40, 100];
var canvas = d3.select("body")
.append("svg")
.attr("width", 500)
.attr("height", 500);
var bars = canvas.selectAll("rect")
.data(dataArray)
.enter()
.append("rect")
.attr("width", function(d){return d;})
.attr("height", 50)
.attr("y", function(d,i){return i*100;});
</script>
</body>
</html>