Bar Chart VI - horizontal linearGradients

This simple bar chart is constructed from a TSV file storing the frequency of letters in the English language. The chart employs conventional margins and a number of D3 features:

d3.tsv - load and parse data
d3.format - format percentages
d3.scale.ordinal - x-position encoding
d3.scale.linear - y-position encoding
d3.max - compute domains
d3.svg.axis - display axes

forked from mbostock's block: Bar Chart

forked from seemantk's block: Bar Chart IV - d3v4

forked from seemantk's block: Bar Chart V - linearGradients

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.bar {
  stop-color: steelblue;
}

.bar.hovered {
  stop-color: brown;
}
.empty {
	stop-opacity: 0;
}

.y.axis path {
  display: none;
}

</style>
<body>
<script src="//d3js.org/d3.v4.min.js"></script>
<script>

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

var y = d3.scaleBand()
    .range([0, height])
		.paddingInner(0.1);

var x = d3.scaleLinear()
    .range([0, width]);
var p = d3.scaleLinear()
		.range([0, 100]);

var yAxis = d3.axisLeft()
    .scale(y)
;

var xAxis = d3.axisBottom()
    .scale(x)
    .ticks(10, "%");

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 + ")");

var defs = d3.select("body svg").append("defs");
  
d3.tsv("data.tsv", type, function(error, data) {
  if (error) throw error;

y.domain(data.map(function(d) { return d.letter; }));
  x.domain([0, d3.max(data, function(d) { return d.frequency; })]);
  p.domain(x.domain());
  
  svg.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);

svg.append("g")
      .attr("class", "y axis")
      .call(yAxis)
    .append("text")
      .attr("transform", "rotate(-90)")
      .attr("y", 6)
      .attr("dy", ".71em")
      .style("text-anchor", "end")
      .text("Frequency");

svg.selectAll(".bar")
      .data(data)
    .enter().append("rect")
      .attr("class", "bar")
      .attr("y", function(d) { return y(d.letter); })
      .attr("height", y.bandwidth())
      .attr("x", 0)
      .attr("width", width)
  		.style("fill", function(d, i) { return "url(#gradient_" + i + ")"; }) 
  		.on("mouseover", function(d, i) {
    			defs.select("#gradient_" + i).selectAll(".bar")
          		.classed("hovered", true)
  			})
  		.on("mouseout", function(d, i) {
    			defs.select("#gradient_" + i).selectAll(".bar")
          		.classed("hovered", false)
  			})
  ;
  defs.selectAll("linearGradient")
  		.data(data)
  	.enter().append("linearGradient")
  		.attr("id", function(d, i) { return "gradient_" + i; })
  		.attr("x1", 0)
  		.attr("x2", 1)
  		.attr("y1", 0)
  		.attr("y2", 0)
  		.each(function(d) {
   				var self = d3.select(this);
    			var stops = ["bar start", "bar end", "empty end"];
    			self.selectAll("stop")
          		.data(stops)
          	.enter().append("stop")
          		.attr("class", function(s, i) { return s; })
          		.attr("offset", function(s, i) {
            			return (i ? p(d.frequency) : "0") + "%";
          			})
         	;
  			})
 	;
});

function type(d) {
  d.frequency = +d.frequency;
  return d;
}

</script>

https://d3js.org/d3.v4.min.js