D3 二维图表的绘制系列（十二）基础散点图

上一篇：南丁格尔图 https://blog.youkuaiyun.com/zjw_python/article/details/98480980

下一篇：多符号散点图 https://blog.youkuaiyun.com/zjw_python/article/details/98483989

代码结构和初始化画布的Chart对象介绍，请先看 https://blog.youkuaiyun.com/zjw_python/article/details/98182540

本图完整的源码地址： https://github.com/zjw666/D3_demo/tree/master/src/scatterChart/basicScatterChart

1 图表效果

在这里插入图片描述

2 数据

3 关键代码

导入数据

d3.csv('./data.csv', function(d){
    return {
        x: +d.x,
        y: +d.y
    };
}).then(function(data){
....

一些样式参数配置

const config = {
        pointColor: chart._colors(0),
        margins: {top: 80, left: 80, bottom: 50, right: 80},
        textColor: 'black',
        gridColor: 'gray',
        ShowGridX: [10, 20, 30, 40, 50, 60, 70 ,80, 90, 100],
        ShowGridY: [10, 20, 30, 40, 50, 60, 70 ,80, 90, 100],
        title: '散点图',
        pointSize: 5,
        hoverColor: 'white',
        animateDuration: 1000
    }

尺度转换，与基础柱状图类似，基础散点图也有X和Y两个轴，且两个轴都是连续的类型

/* ----------------------------尺度转换------------------------  */
    chart.scaleX = d3.scaleLinear()
                    .domain([0, Math.ceil(d3.max(data, (d) => d.x)/10)*10])
                    .range([0, chart.getBodyWidth()])
    
    chart.scaleY = d3.scaleLinear()
                    .domain([0, Math.ceil(d3.max(data, (d) => d.y)/10)*10])
                    .range([chart.getBodyHeight(), 0])

渲染数据点，很简单，用circle元素就可以了

/* ----------------------------渲染数据点------------------------  */
    chart.renderPoints = function(){
        let points = chart.body().selectAll('.point')
                    .data(data);

            points.enter()
                    .append('circle')
                    .classed('point', true)
                .merge(points)
                    .attr('cx', (d) => chart.scaleX(d.x))
                    .attr('cy', (d) => chart.scaleY(d.y))
                    .attr('r', 0)
                    .attr('fill', config.pointColor)
                    .transition().duration(config.animateDuration)
                    .attr('r', config.pointSize)
            
            points.exit()
                    .remove();
    }

渲染坐标轴、文本标签和网格，这些与基础柱状图几乎相同

/* ----------------------------渲染坐标轴------------------------  */
    chart.renderX = function(){
        chart.svg().insert('g','.body')
                .attr('transform', 'translate(' + chart.bodyX() + ',' + (chart.bodyY() + chart.getBodyHeight()) + ')')
                .attr('class', 'xAxis')
                .call(d3.axisBottom(chart.scaleX));
    }

    chart.renderY = function(){
        chart.svg().insert('g','.body')
                .attr('transform', 'translate(' + chart.bodyX() + ',' + chart.bodyY() + ')')
                .attr('class', 'yAxis')
                .call(d3.axisLeft(chart.scaleY));
    }

    chart.renderAxis = function(){
        chart.renderX();
        chart.renderY();
    }

    /* ----------------------------渲染文本标签------------------------  */
    chart.renderText = function(){
        d3.select('.xAxis').append('text')
                            .attr('class', 'axisText')
                            .attr('x', chart.getBodyWidth())
                            .attr('y', 0)
                            .attr('fill', config.textColor)
                            .attr('dy', 30)
                            .text('X');

        d3.select('.yAxis').append('text')
                            .attr('class', 'axisText')
                            .attr('x', 0)
                            .attr('y', 0)
                            .attr('fill', config.textColor)
                            .attr('dx', '-30')
                            .attr('dy', '10')
                            .text('Y');
    }

    /* ----------------------------渲染网格线------------------------  */
    chart.renderGrid = function(){
        d3.selectAll('.yAxis .tick')
            .each(function(d, i){
                if (config.ShowGridY.indexOf(d) > -1){
                    d3.select(this).append('line')
                        .attr('class','grid')
                        .attr('stroke', config.gridColor)
                        .attr('x1', 0)
                        .attr('y1', 0)
                        .attr('x2', chart.getBodyWidth())
                        .attr('y2', 0);
                }
            });

        d3.selectAll('.xAxis .tick')
            .each(function(d, i){
                if (config.ShowGridX.indexOf(d) > -1){
                    d3.select(this).append('line')
                        .attr('class','grid')
                        .attr('stroke', config.gridColor)
                        .attr('x1', 0)
                        .attr('y1', 0)
                        .attr('x2', 0)
                        .attr('y2', -chart.getBodyHeight());
                }
            });
    }

绑定鼠标交互事件，鼠标悬停时显示坐标值

/* ----------------------------绑定鼠标交互事件------------------------  */
    chart.addMouseOn = function(){
        //防抖函数
        function debounce(fn, time){
            let timeId = null;
            return function(){
                const context = this;
                const event = d3.event;
                timeId && clearTimeout(timeId)
                timeId = setTimeout(function(){
                    d3.event = event;
                    fn.apply(context, arguments);
                }, time);
            }
        }

        d3.selectAll('.point')
            .on('mouseover', function(d){
                const e = d3.event;
                const position = d3.mouse(chart.svg().node());
                e.target.style.cursor = 'hand'

                d3.select(e.target)
                    .attr('fill', config.hoverColor);
                
                chart.svg()
                    .append('text')
                    .classed('tip', true)
                    .attr('x', position[0]+5)
                    .attr('y', position[1])
                    .attr('fill', config.textColor)
                    .text('x: ' + d.x + ', y: ' + d.y);
            })
            .on('mouseleave', function(){
                const e = d3.event;
                
                d3.select(e.target)
                    .attr('fill', chart._colors(0));
                    
                d3.select('.tip').remove();
            })
            .on('mousemove', debounce(function(){
                    const position = d3.mouse(chart.svg().node());
                    d3.select('.tip')
                    .attr('x', position[0]+5)
                    .attr('y', position[1]-5);
                }, 6)
            );
    }