d3.svg.line.radial()

HTML

<script src="http://d3js.org/d3.v2.js"></script>

CSS

.line {
  fill: none;
  stroke: steelblue;
  stroke-width: 1.5px;
}

JavaScript

var radius = 100,
    padding = 10,
    degreeToRadians = Math.PI/180;

var dimension = (2 * radius) + (2 * padding),
    angles = [0,45,90,135]; //array of angles


var line = d3.svg.line.radial()
    .interpolate("basis-open")
    //.interpolate("cardinal-open")
    .tension(0)
    .radius(radius) //constant radius
    .angle(function(d, i) { return d * degreeToRadians; }); //angle is the value in the array

var svg = d3.select("body").append("svg")
    .attr("width", dimension)
    .attr("height", dimension)
.append("g");

svg.append("path").datum(angles)
    .attr("class", "line")
    .attr("d", line)
    .attr("transform", "translate(" + (radius + padding) + ", " + (radius + padding) + ")");