Question

我正在实施经典的mercator示例（https://github.com/mbostock/d3/blob/master/examples/mercator/mercator.html），我已将其更改为放大到阿富汗并仅使用一个自定义滑块。我正在阅读发生爆炸的地方的GeoJSON数据，图表将它们全部映射到负载。我想使用滑块一次仅查看一个月的爆炸点，但是在过滤结果时遇到问题。我已根据Google群组中的帖子尝试过多项内容，但未能了解如何过滤先前从'explosionions.json'中读取的数据。谢谢你的帮助！

    <!DOCTYPE html>
    <html>
    <head>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8">
<title>IED Attacks in Afghanistan (2004-2009)</title>
<script type="text/javascript" src="../d3.v2.js"></script>
<script type="text/javascript" src="../lib/jquery/jquery.min.js"></script>
<script type="text/javascript" src="../lib/jquery-ui/jquery-ui.min.js"></script>
<style type="text/css">

    @import url("../lib/jquery-ui/jquery-ui.css");

    body, .ui-widget {
    font: 14px Helvetica Neue;
    }

    svg {
    width: 960px;
    height: 600px;
    border: solid 1px #ccc;
    background: #eee;
    }

    line {
    stroke: brown;
    stroke-dasharray: 4,2;
    }

    path {
    fill: #ccc;
    stroke: #fff;
    }

    div {
    width: 960px;
    }

</style>
</head>
<body>
<h3>IED Attacks in Afghanistan (2004-2009)</h3>
<script type="text/javascript">

        // Create the Mercator Projection (Map)
        var xy = d3.geo.mercator(),
            path = d3.geo.path().projection(xy);


        // Create the states variable
        var states = d3.select("body")
        .append("svg")
        .append("g")
            .attr("id", "states");
        // Create the equator variable
        var equator = d3.select("svg")
        .append("line")
            .attr("x1", "0%")
            .attr("x2", "100%");
        // Create the explosions variable
        var explosions = d3.select("svg")
        .append("g")
            .attr("id","explosions");

        // Load in the states & equator data from the file 'world-countries.json'
        d3.json("world-countries.json", function(collection) {
            states
                .selectAll("path")
                .data(collection.features)
                .enter().append("path")
                .attr("d", path)
                .append("title")
                .text(function(d) { return d.properties.name; });
            equator
                .attr("y1", xy([0, 0])[1])
                .attr("y2", xy([0, 0])[1]);
        });

        // the variable that holds our translate, center on Afghanistan
        var translate = xy.translate(); //create translation to center gride in different area
        translate[0] = -1741;
        translate[1] = 1487;
        xy.translate(translate); // center

        xy.scale(12000); //zoom in

        // Load in the explosions data from the file 'explosions.json'
        d3.json("explosions.json", function(collection) {
            explosions
                .selectAll("path") //make a path and attach data
                .data(collection.features)
                .enter().append("path")
                .attr("d", path)
                .style("stroke","red") //color the path points
                .style("stroke-width",2) //size of point stroke
                .attr("class","explosionpoint")
                .append("title") //title is the 'name' field in the json file
                .text(function(d) { return d.properties.name; });
        });



    </script>

    <p></p>
    <!-- Slider -->
    <div id="scale"></div><p></p>
    <script type="text/javascript">

        $("#scale").slider({
        min: 20040101, //min : 1/1/04
        max: 20100101, //max: 1/1/10
        value: 20060601, //default slider value
        step: 100, // step is the allow increments the slider can move. 100 = one month
        slide: function(event, ui) {


            /* REMOVE ALL EXPLOSION PATHS EXCEPT FOR A PARTICULAR MONTH OR RELOAD WITH FILTERED RESULTS */
        }
        });

</script>

Answer 1

您需要发布部分或全部的explosionions.json对象以获得具体答案。但是，如果JSON的结构类似于{explosion1:{data1:true, data2:true}, explosion2:{data1:true, data2:false}}：

，则此类内容将过滤JSON

function filterJSON(json, key, value) {
  var result = {};
  for (var explosionIndex in json) {
    if (json[explosionIndex][key] === value) {
      result[explosionIndex] = json[explosionIndex];
    }
  }
  return result;
}

（例如filterJSON(myjson, "data1", true)将为所有爆炸提供data1：true）

这不是d3特有的。

然后你可以在d3方面使用类似的东西：

explosions.data(myFilteredData).exit().remove(); // remove ones you don't want
explosions.enter().append("path")... // add back ones you do want

如果我了解您的应用程序，那么切换SVG元素的visiblity属性实际上会更好。

var sliderrange = [20040101, 20040201]; //replace with code based on your slider
explosions.selectAll(".explosionpoint").attr("visibility", function(d) {
  //Replace with the correct date comparison logic
  return d.date < sliderrange[1] && d.date > sliderrange[0] ? "visible" : "hidden";
});

Answer 2

D3确实有一种非常自然的方式。我假设你的数据看起来像这样：

[{name: explosion1name, day: 20040110,...}, {name: explosion2name, day: 20040111,...}]

...并且您已经获得了一些变量，我们将其称为explosionsData，以引用数据。

然后，您可以使用从滑块中获取值的函数绘制爆炸。请参阅下面添加的.filter。

function drawExplosions(startDay, endDay) {
    explosions.selectAll("path") //make a path and attach data
            .data(collection.features)
            .enter().append("path")
            .filter( function (d) { return ( (d.day > startDay) && (d.day < endDay) )})
            .attr("d", path)
            .style("stroke","red") //color the path points
            .style("stroke-width",2) //size of point stroke
            .attr("class","explosionpoint")
            .append("title") //title is the 'name' field in the json file
            .text(function(d) { return d.properties.name; });

只要滑块值发生变化，就可以调用此函数。

D3过滤数据点

2 个答案: