//確定畫布的大小var width = 400;var height = 400;//在 body 里添加一個 SVG 畫布 var svg = d3.select("body")  .append("svg")  .attr("width", width)  .attr("height", height);//定義畫布周圍空白的地方var padding = {left: 30, right: 30, top: 20, bottom: 20};//定義一個數組var dataset = [10, 20, 30, 40, 30, 20, 10, 5];//x軸的比例尺var xScale = d3.scale.ordinal()  .domain(d3.range(dataset.length))  .rangeRoundBands([0, width - padding.left - padding.right]);//y軸的比例尺var yScale = d3.scale.linear()  .domain([0, d3.max(dataset)])  .range([height - padding.top - padding.bottom, 0]);//定義x軸var xAxis = d3.svg.axis()  .scale(xScale)  .orient("bottom");//定義y軸var yAxis = d3.svg.axis()  .scale(yScale)  .orient("left");//矩形之間的空白var rectPadding = 4;//添加矩形元素var rects = svg.selectAll(".MyRect")  .data(dataset)  .enter()  .append("rect")  .attr("class", "MyRect")  .attr("fill", "steelblue")  .attr("transform", "translate(" + padding.left + "," + padding.top + ")")  .attr("x", function (d, i) {   return xScale(i) + rectPadding / 2;  })  .attr("y", function (d) {   return yScale(d);  })  .attr("width", xScale.rangeBand() - rectPadding)  .attr("height", function (d) {   return height - padding.top - padding.bottom - yScale(d);  });//添加文字元素var texts = svg.selectAll(".MyText")  .data(dataset)  .enter()  .append("text")  .attr("class", "MyText")  .attr("fill", "white")  .attr("text-anchor", "middle")  .attr("transform", "translate(" + padding.left + "," + padding.top + ")")  .attr("x", function (d, i) {   return xScale(i) + rectPadding / 2;  })  .attr("y", function (d) {   return yScale(d);  })  .attr("dx", function () {   return (xScale.rangeBand() - rectPadding) / 2;  })  .attr("dy", function (d) {   return 20;  })  .text(function (d) {   return d;  });//添加x軸svg.append("g")  .attr("class", "axis")  .attr("transform", "translate(" + padding.left + "," + (height - padding.bottom) + ")")  .call(xAxis);//添加y軸svg.append("g")  .attr("class", "axis")  .attr("transform", "translate(" + padding.left + "," + padding.top + ")")  .call(yAxis);