var rand = d3.random.normal(0,25); 
var dataset = []; 
for(var i=0;i<100;i++){ 
 dataset.push( rand() ); 
} 

var bin_num = 15; 
var histogram = d3.layout.histogram() 
   .range([-50,50]) 
    .bins(bin_num) 
   .frequency(true); 

var data = histogram(dataset); 

var max_height = 400; 
var rect_step = 30; 
var heights = []; 
for(var i=0;i<data.length;i++){ 
 heights.push( data[i].y ); 
} 
var yScale = d3.scale.linear() 
     .domain([d3.min(heights),d3.max(heights)]) 
     .range([0,max_height]); 

//绘制图形 
var graphics = svg.append("g") 
     .attr("transform","translate(30,20)"); 
 
//绘制矩形 
graphics.selectAll("rect") 
  .data(data) 
  .enter() 
  .append("rect") 
  .attr("x",function(d,i){ 
   return i * rect_step; 
  }) 
  .attr("y", function(d,i){ 
   return max_height - yScale(d.y); 
  }) 
  .attr("width", function(d,i){ 
   return rect_step - 2; 
  }) 
  .attr("height", function(d){ 
   return yScale(d.y); 
  }) 
  .attr("fill","steelblue"); 
 
//绘制坐标轴的直线 
graphics.append("line") 
  .attr("stroke","black") 
  .attr("stroke-width","1px") 
  .attr("x1",0) 
  .attr("y1",max_height) 
  .attr("x2",data.length * rect_step) 
  .attr("y2",max_height); 
 
//绘制坐标轴的分隔符直线 
graphics.selectAll(".linetick") 
  .data(data) 
  .enter() 
  .append("line") 
  .attr("stroke","black") 
  .attr("stroke-width","1px") 
  .attr("x1",function(d,i){ 
   return i * rect_step + rect_step/2; 
  }) 
  .attr("y1",max_height) 
  .attr("x2",function(d,i){ 
   return i * rect_step + rect_step/2; 
  }) 
  .attr("y2",max_height + 5); 
 
//绘制文字 
graphics.selectAll("text") 
  .data(data) 
  .enter() 
  .append("text") 
  .attr("font-size","10px") 
  .attr("x",function(d,i){ 
   return i * rect_step; 
  }) 
  .attr("y", function(d,i){ 
   return max_height; 
  }) 
  .attr("dx",rect_step/2 - 8) 
  .attr("dy","15px") 
  .text(function(d){ 
   return Math.floor(d.x); 
  });