Question

我正在使用D3.js绘制svg行。我想通过在添加到行路径之前删除重复的（x，y）点来提高性能。在D3或javascript中执行此操作的最佳方法是什么。我正在从json文件加载数据，用于此测试，但稍后它可能会在服务器上的数组中出现。

请参阅下面的代码片段和控制台输出。

感谢您的帮助

        var x = d3.scale.linear().domain([xMin, xMax]).rangeRound([0, width]);
        var y = d3.scale.linear().domain([yMin, yMax]).rangeRound([height, 0]);

        var line = d3.svg.line()
            .x(function(d, i) { 
                var xPoint = x((i + 1) * xMult);
                console.log("xPoint= " + xPoint.toString()); 
                return xPoint; })
            .y(function(d) { 
                var yPoint = y(d);
                console.log("yPoint= " + yPoint.toString()); 
                return yPoint; })
            .interpolate("basis-open")
            .tension(0);


            ...


        // Add the valueline path.
        g.append("path")
            .attr("class", "line")
            .attr("d", line(data));


--------------------------------------------------
Console Output from two lines in code above
console.log("xPoint= " + xPoint.toString()); 
console.log("yPoint= " + yPoint.toString());
----------------------------------------------

xPoint= 0
yPoint= 24
xPoint= 0
yPoint= 24
xPoint= 1
yPoint= 24
xPoint= 1
yPoint= 24
xPoint= 1
yPoint= 24
xPoint= 1
yPoint= 24
xPoint= 2
yPoint= 24
xPoint= 2
yPoint= 25
xPoint= 2
yPoint= 25
xPoint= 2
yPoint= 24
xPoint= 3
yPoint= 25
xPoint= 3
yPoint= 25
xPoint= 3
yPoint= 25
xPoint= 3
yPoint= 25
xPoint= 4
yPoint= 25

Answer 1

uniq的问题在于，无论它们在数组中的位置如何，都要删除重复的点。对于点或点线的多边形，您只想删除连续的重复点。以下是使用JavaScript执行此操作的示例。

var point1 = { x: 0, y: 24 };
var point2 = { x: 1, y: 24 };
var point3 = { x: 2, y: 24 };
var point4 = { x: 2, y: 25 };

var points = [point1, point1, 
              point2, point2, point2, point2, 
              point3, 
              point4, point4, 
              point3];

var pointsAreEqual = function(point1, point2) {
    return point1.x === point2.x && point1.y === point2.y;
}

var removeConsecDupes = function(items, itemsAreEqual) {
    var previous, results = []; 

    var callback = function(value, index) {
        if (index === 0 || !itemsAreEqual(previous, value)) {
            results.push(value);
        }   
        previous = value;
    }   
    items.forEach(callback);

    return results;
}

var results = removeConsecDupes(points, pointsAreEqual);

console.dir(results);

结果：

[ { x: 0, y: 24 },
  { x: 1, y: 24 },
  { x: 2, y: 24 },
  { x: 2, y: 25 },
  { x: 2, y: 24 } ]

Answer 2

我使用underscore _.uniq method传递自定义迭代器函数（如JS {} !== {}中所示）。

像这样的东西（适合你自己的背景）

_.uniq(data, false, function( d1, d2 ) {
    return (d1.x === d2.x && d1.y === d1.y);
});

d3行过滤掉（删除）重复点

2 个答案: