bar chart

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>D3 Page Template</title>
<script src="https://d3js.org/d3.v4.min.js"></script>
</head>
<body>
	<style>
.axis path,
.axis line{
    fill: none;
    stroke: black;
    shape-rendering: crispEdges;
}

.axis text {
    font-family: sans-serif;
    font-size: 11px;
}
</style>
<script type="text/javascript">
// Your beautiful D3 code will go here
var width = 1200;  //画布的宽度
var height = 600;   //画布的高度
var svg = d3.select("body")     //选择文档中的body元素
    .append("svg")          //添加一个svg元素
    .attr("width", width)       //设定宽度
    .attr("height", height);    //设定高度   
var padding = {left:45, right:40, top:25, bottom:20};

d3.csv("file1.csv",function(csvdata) {  
var dataset = []
var employee = []
var average = 0
for (var i = 0; i < csvdata.length - 3; i++) {
    dataset.push(csvdata[i].Number_of_people)
 employee.push(csvdata[i].Highest_level_completed)
}    
average = (csvdata[csvdata.length - 3].Number_of_people)
var xScale = d3.scaleBand()
    .domain(employee)
	.range([0, width - padding.left - padding.right])
    .paddingInner(0)
    .paddingOuter(0); 
var yScale =  d3.scaleLinear()
    .domain([0,d3.max(dataset)])
    .range([height - padding.top - padding.bottom, 0]);
//定义x轴
var xAxis = d3.axisBottom(xScale)

//定义y轴
var yAxis = d3.axisLeft(yScale)

var rectPadding = 4;

svg.append("line")
    .attr("x1",padding.left)
    .attr("y1", padding.top  + yScale(average))
    .attr("x2",width - padding.right)
    .attr("y2", padding.top  + yScale(average))
    .attr("stroke-width",3)
    .attr("stroke","red");

svg.append("g")
  .attr("class","axis")
  .attr("transform","translate(" + padding.left + "," + (height - padding.bottom) + ")")
  .call(xAxis);

//添加y轴
svg.append("g")
  .attr("class","axis")
  .attr("transform","translate(" + padding.left + "," + padding.top + ")")
  .call(yAxis)
  .append("text")
    .attr("transform", "rotate(-90)")
    .attr("y", 6)
    .attr("dy", ".71em")
    .style("fill","black")    
    .text("Number of people");;  
  
  
var legend = svg.selectAll(".legend")
      .data(average)
    	.enter().append("g")
      .attr("class", "legend")
      .attr("transform","translate(0,20)" )

legend.append("rect")
      .attr("x", width - 28)
      .attr("width", 28)
      .attr("height", 8)
      .style("fill", 'red');

legend.append("text")
      .attr("x", width-34)
      .attr("y", 2)
      .attr("dy", ".35em")
      .style("text-anchor", "end")
      .text('average number of people');
});

</script>
</body>
</html>

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