d3行过滤掉（删除）复制点

Question

我使用D3.js绘制svg行。我想通过在添加到行路径之前移除重复（x，y）点来提高性能。在D3或javascript中完成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，但它可能会在服务器中的数组中出现。

请参阅下面的代码片段和控制台输出。

感谢所有帮助

 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

我会用underscore _.uniq method传递一个自定义的迭代函数（如JS {} !== {}）。

像这样的东西（适用于你自己的上下文）

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

Answer 2

与uniq的问题是，虽然你无论在阵列中的定位的删除重复点。对于点或点的多边形，您只需要删除连续的重复点。这里是一个如何使用JavaScript来做到这一点的例子。

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 } ]