d3 simple line graph, showing 'step-after' interpolation

This example shows a problem with the 'step-after' interpolation. It does not draw the 'last' step -- i.e., the step for the last data point. starting from bostock's example. then using different interpolation. and without an url for data.

CSS

body {
  font: 10px sans-serif;
}

.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}

.x.axis path {
  display: none;
}

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

JavaScript

var margin = {top: 20, right: 20, bottom: 30, left: 40},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

/* 
 * value accessor - returns the value to encode for a given data object.
 * scale - maps value to a visual display encoding, such as a pixel position.
 * map function - maps from data value to display value
 * axis - sets up axis
 */ 

// setup x 
var xValue = function(d) { return d.Calories;}, // data -> value
    xScale = d3.scale.linear().range([0, width]), // value -> display
    xMap = function(d) { return xScale(xValue(d));}, // data -> display
    xAxis = d3.svg.axis().scale(xScale).orient("bottom");

// setup y
var yValue = function(d) { return d["Protein (g)"];}, // data -> value
    yScale = d3.scale.linear().range([height, 0]), // value -> display
    yMap = function(d) { return yScale(yValue(d));}, // data -> display
    yAxis = d3.svg.axis().scale(yScale).orient("left");

// setup fill color
var cValue = function(d) { return d.Manufacturer;},
    color = d3.scale.category10();

// add the graph canvas to the body of the webpage
var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

// add the tooltip area to the webpage
var tooltip = d3.select("body").append("div")
    .attr("class", "tooltip")
    .style("opacity", 0);

// load data
d3.csv("cereal.csv", function(error, data) {

  // change string (from CSV) into number format
  data.forEach(function(d) {
    d.Calories = +d.Calories;
    d["Protein (g)"] = +d["Protein (g)"];
//    console.log(d);
  });

  // don't want dots overlapping axis, so add in buffer to data domain
  xScale.domain([d3.min(data, xValue)-1, d3.max(data, xValue)+1]);
  yScale.domain([d3.min(data, yValue)-1, d3.max(data, yValue)+1]);

  // x-axis
  svg.append("g")
      .attr("class", "x...