使用数据中的d3显示圆

Question

In this fiddle I'm attempting to draw circles read from a file :

http://jsfiddle.net/zzz8svuq/17/

But no circles are appearing.

Here I am binding the data to svg :

    svg.data(data)
            .enter().append("circle")
            .attr("stroke", "red")
            .attr("stroke-width" , "2px")
            .attr("cx", xMap)

This is not correct ?

fiddle code :

 var data = d3.csv.parse( d3.select("pre#data").text() );

        var margin = {top: 20, right: 20, bottom: 130, left: 140},
                width = 960 - margin.left - margin.right,
                height = 500 - margin.top - margin.bottom;

        var svg = d3.select("body").append("svg")
                .attr("width", 500)
                .attr("height",500)
                .append("g");

        var xValue = function (data) {
            return data.x;
        }

        xScale = d3.scale.linear().range([0, width - margin.left - margin.right]) // value -> display

        xMap = function (d) {
            return xScale(xValue(d));
        }

        svg.data(data)
                .enter().append("circle")
                .attr("stroke", "red")
                .attr("stroke-width" , "2px")
                .attr("cx", xMap)

<pre style="display:none" id="data">
    label,x,y,r
l1,100,30,50
l2,5,5,100
l3,50,50,20
</pre>

    body {
        font: 11px sans-serif;
    }

    .axis path,
    .axis line {
        fill: none;
        stroke: #000;
        shape-rendering: crispEdges;
    }

Update :

Added

.attr("cy", 5)
.attr("r", 5)

but same result

Answer 1

circles need 3 attributes cx, cy (the position) and r (the radius). You are not supplying cy or r and r defaults to 0 which means your circles are not rendered.

Answer 2

If you want to append circles to a container from json data, you will have bind the data to a selection inside the container instead of bind data to the container. Try this way.

svg.selectAll("circle")
     .data(data)
     .enter().append("circle")
     .attr("stroke", "red")
     .attr("stroke-width" , "2px")
     .attr("cx", xMap) //Center point X
     .attr("cy", yMap) // Center point Y
     .attr("r", 5); //Radius

Confirm that cx, cy and r attributes are valid.