D3 Examples - Stuck with Y-Axis Mapping

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<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8">
        <title>Loading CSV Data with D3</title>
        <script type="text/javascript" src="https://d3js.org/d3.v3.js"></script>
        <style type="text/css">
​
            body    {
                background-color: #FDD8FF;
                font-family: Arial;
                font-size: 25px;
                text-align: center;
​
            }
        
            p {
                font-size: 40px;
                text-align: left;
            }
​
​
            svg {
                background-color: #FDD8FF;
                fill: gray;
            }
​
            .axis path,
            .axis line {
                fill: none;
                stroke: black;
                shape-rendering: crispEdges;
            }
​
            .axis text {
                font-family: sans-serif;
                font-style: 11px;
            }
​
            rect:hover  {
                fill: #79007F;
            }
​
            g.bar text {
                fill: black;
                font-size: 10px;
                text-anchor: end;
            }
            
        </style>
    </head>
    <body>
        <p>Hospitals' Productive Hours per Patient, CA 2013</p>
        
​
        <script type="text/javascript">
​
​
            var w = 400;
            var h = 800;
            var padding = [ 20, 10, 30, 150 ] //top, right, bottom, left
​
​
            var widthScale = d3.scale.linear()
                                .range([0, w - padding[1] - padding[3] ]);
​
​
            var heightScale = d3.scale.ordinal()
                                .rangeRoundBands([ padding[0], h - padding[2] ], 0.1);
​
​
            var colorScale = d3.scale.ordinal()
                                .domain(["Sacramento", "Alameda", "Los Angeles"])
                                .range(["orange", "blue", "green"]);
​
​
            var xAxis = d3.svg.axis()
                            .scale(widthScale)
                            .orient("bottom");
​
​
            var yAxis = d3.svg.axis()
                            .scale(heightScale)
                            .orient("left");
​
​
            var svg = d3.select("body")
                        .append("svg")
                        .attr("width", w)
                        .attr("height", h);
​
​
​
            d3.csv("hospitalStaffing.csv", function(data) {
​
​
                data.sort(function(a, b) {
                    return d3.descending(+a.ProductiveHoursPatient, +b.ProductiveHoursPatient);
                });
​
                widthScale.domain([ 0, d3.max(data, function(d) {
                    return +d.ProductiveHoursPatient;
                }) ]);
​
                heightScale.domain(d3.range(data.length));
                console.log(heightScale.domain());
​
                var groups = svg.selectAll("g.bar")
                                .data(data)
                                .enter()
                                .append("g")
                                .attr("class", "bar");
​
                groups.append("rect")
                    .attr("x", padding[3])
                    .attr("y", function(d, i) {
                        return heightScale(i);
                    })
                    .attr("width", function(d) {
                        return widthScale(d.ProductiveHoursPatient);
                    })
                    .attr("height", heightScale.rangeBand())
                    .attr("fill", function(d) {
                        return colorScale(d.County);
                    });
​
                groups.append("text")
                    .attr("x", padding[3] - 3)
                    .attr("y", function(d, i) {
                        return heightScale(i) + 10;
                    })
                    .text(function(d) {
                        return d.County;
                    });
​
                groups.append("title")
                    .text(function(d) {
                        return d.Facility + ": " + d.ProductiveHoursPatient;
                    });
​
                svg.append("g")
                    .attr("class", "x axis")
                    .attr("transform", "translate(" + padding[3] + "," + (h - padding[2]) + ")")
                    .call(xAxis);
​
                // svg.append("g")
                //  .attr("class", "y axis")
                //  .attr("transform", "translate(" + (padding[3] - 5) + ",0)")
                //  .call(yAxis);
​
            });
​
        
        </script>
​
    </body>
</html>
    