d3.js节点和链接

Question

我正在尝试使节点连接到线路，并能够在拖动时四处移动。 我知道我需要将鼠标移至上方，移至下方，移至下方并移至上方。 但是，我无法弄清楚如何使用d3.js进行此操作，因为我从未做过。 到目前为止，这是我所做的。

window.onload = function () {
    var drawOptions = {
        // dimensions of svg element 
        SVG_WIDTH: 800,
        SVG_HEIGHT: 600,
        SHRINK_FACTOR: 100,
        BIG_CIRCLE: 200
    };

    // 1. array of objects representing the network
    //    each object is a province or state
    //    preliminary version - only 2 provinces, 1 state

    var provincesAndStates = [
        {
            name: 'Ontario',
            sym: 'ON',
            country: 'Canada',
            pop: 13873933
        },
        {
            name: 'Quebec',
            sym: 'QC',
            country: 'Canada',
            pop: 8294656
        },
        {
            name: 'New York',
            sym: 'NY',
            country: 'USA',
            pop: 19795791
        },
        {
            name: 'Michigan',
            sym: 'MI',
            country: 'USA',
            pop: 30795791
        },
        {
            name: 'Georgia',
            sym: 'GA',
            country: 'USA',
            pop: 20795791
        },
        {
            name: 'Alabama',
            sym: 'Al',
            country: 'USA',
            pop: 1700000
        },
        {
            name: 'California',
            sym: 'CA',
            country: 'USA',
            pop: 2000000
        },
        {
            name: 'Florida',
            sym: 'Fl',
            country: 'USA',
            pop: 2500000
        },
        {
            name: 'Texas',
            sym: 'TX',
            country: 'USA',
            pop: 3100000
        },
        {
            name: 'Tenesse',
            sym: 'TN',
            country: 'USA',
            pop: 7000000
        },
        {
            name: 'Newfoundland',
            sym: 'NFL',
            country: 'USA',
            pop: 1600000
        }
    ];

    var connections = [
        {
            source: 'ON',
            target: 'QC'
        },
        {
            source: 'ON',
            target: 'NY'
        },
        {
            source: 'QC',
            target: 'NY'
        },
        {
            source: 'TN',
            target: 'NFL'
        },
        {
            source: 'Al',
            target: 'GA'
        }
    ];

    d3.select('#graphicsContainer')
        .append('svg')
        .attr('width', drawOptions.SVG_WIDTH)
        .attr('height', drawOptions.SVG_HEIGHT);

    // Circle

    d3.select('svg').selectAll('circle').data(provincesAndStates).enter().append('circle')
        .attr('id', function (d, i) { return provincesAndStates[i].sym });

    d3.select('svg').selectAll('circle')
        .attr('r', function (d, i) { return Math.sqrt(d.pop) / drawOptions.SHRINK_FACTOR })
        .attr('cx', function (d, i) {
            return drawOptions.SVG_WIDTH / 2 + drawOptions.BIG_CIRCLE * Math.sin(i * 2 * Math.PI / provincesAndStates.length);
        })
        .attr('cy', function (d, i) {
            return drawOptions.SVG_HEIGHT / 2 + drawOptions.BIG_CIRCLE * Math.cos(i * 2 * Math.PI / provincesAndStates.length);
        })

    d3.select('svg').selectAll('line').data(connections).enter().append('line')
        .attr('id', function (d, i) { return d.source + '-' + d.target });

    d3.select('svg').selectAll('line')
        .attr('x1',
        function (d, i) {
            var srcCircle = d3.select('#' + d.source);
            return srcCircle.attr('cx');
        })
        .attr('y1', function (d, i) {
            var srcCircle = d3.select('#' + d.source);
            return srcCircle.attr('cy');
        })
        .attr('x2', function (d, i) {
            var tgtCircle = d3.select('#' + d.target);
            return tgtCircle.attr('cx');
        })

        .attr('y2', function (d, i) {
            var tgtCircle = d3.select('#' + d.target);
            return tgtCircle.attr('cy');
        })

    // D R A G G I N G    C I R C L E S

    d3.selectAll('circle').call(d3.drag().on('drag', dragCircle));

    function dragCircle(d) {
        var thisCircle = d3.select(this);
        thisCircle.attr('cx', d3.event.x).attr('cy', d3.event.y);
    }
};