我正在做一个简单的圆环图。我按预期提供数据并生成甜甜圈。此外，在远处添加标签。现在，我想在标签中添加直线到圆弧的中心。但是，我没有收到任何错误，我也没有看到任何错误。请帮忙！
SNIPPET：
//module declaration
var app = angular.module('myApp',[]);
//Controller declaration
app.controller('myCtrl',function($scope){
$scope.svgWidth = 800; //svg Width
$scope.svgHeight = 500; //svg Height
//Data in proper format
var data = [{
"letter": "A",
"frequency": "60"
}, {
"letter": "B",
"frequency": "30"
}, {
"letter": "C",
"frequency": "10"
}];
//removing prior svg elements ie clean up svg
d3.select('svg').selectAll("*").remove();
//resetting svg height and width in current svg
d3.select("svg").attr("width", $scope.svgWidth).attr("height", $scope.svgHeight);
//Setting up of our svg with proper calculations
var svg = d3.select("svg");
var margin = {top: 20,right: 20,bottom: 30,left: 40};
var width = svg.attr("width") - margin.left - margin.right;
var height = svg.attr("height") - margin.top - margin.bottom;
var radius = 200;
//Plotting our base area in svg in which chart will be shown
var g = svg.append("g").attr("transform", "translate(" + width / 2 + "," + height / 2 + ")");
var pie = d3.pie().sort(null)
.value(function(d) {return d.frequency;});
var piedata = pie(data);
var arc = d3.arc()
.innerRadius(radius - 100)
.outerRadius(radius - 50);
var path = g.selectAll("path")
.data(piedata)
.enter().append("path")
.attr("fill", function() {
return "hsl(" + Math.random() * 360 + ",100%,50%)";
})
.attr("d", arc);
g.selectAll("text").data(piedata)
.enter()
.append("text")
.attr("text-anchor", "middle")
.attr("x", function(d) {
var a = d.startAngle + (d.endAngle - d.startAngle) / 2 - Math.PI / 2;
d.cx = Math.cos(a) * (radius - 75);
return d.x = Math.cos(a) * (radius - 20);
})
.attr("y", function(d) {
var a = d.startAngle + (d.endAngle - d.startAngle) / 2 - Math.PI / 2;
d.cy = Math.sin(a) * (radius - 75);
return d.y = Math.sin(a) * (radius - 20);
})
.text(function(d) {
return d.data.letter;
});
var polyline = g.select(".lines")
.selectAll("polyline")
.data(pie(data), function(d){ return d.data.letter });
polyline.enter().append("polyline");
}); <head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.4.12/angular.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.3.0/d3.min.js"></script>
</head>
<body ng-app="myApp" ng-controller="myCtrl">
<svg></svg>
</body>
参考：
答案 0 :(得分：2)
查看链接的示例，作者介绍了一个辅助函数来计算弧外的角度，然后使用polyline绘制。窃取他们的实现并将其应用到您的图表看起来像这样：
<!DOCTYPE html>
<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.3.0/d3.min.js"></script>
</head>
<body ng-app="myApp" ng-controller="myCtrl">
<svg></svg>
<script>
//module declaration
//var app = angular.module('myApp', []);
//Controller declaration
//app.controller('myCtrl', function($scope) {
var $scope = {};
$scope.svgWidth = 800; //svg Width
$scope.svgHeight = 500; //svg Height
//Data in proper format
var data = [{
"letter": "A",
"frequency": "60"
}, {
"letter": "B",
"frequency": "30"
}, {
"letter": "C",
"frequency": "10"
}];
//removing prior svg elements ie clean up svg
d3.select('svg').selectAll("*").remove();
//resetting svg height and width in current svg
d3.select("svg").attr("width", $scope.svgWidth).attr("height", $scope.svgHeight);
//Setting up of our svg with proper calculations
var svg = d3.select("svg");
var margin = {
top: 20,
right: 20,
bottom: 30,
left: 40
};
var width = svg.attr("width") - margin.left - margin.right;
var height = svg.attr("height") - margin.top - margin.bottom;
var radius = 200;
//Plotting our base area in svg in which chart will be shown
var g = svg.append("g").attr("transform", "translate(" + width / 2 + "," + height / 2 + ")");
var pie = d3.pie().sort(null)
.value(function(d) {
return d.frequency;
});
var piedata = pie(data);
var arc = d3.arc()
.innerRadius(radius - 100)
.outerRadius(radius - 50);
var outerArc = d3.arc()
.innerRadius(radius * 0.9)
.outerRadius(radius * 0.9);
var path = g.selectAll("path")
.data(piedata)
.enter().append("path")
.attr("fill", function() {
return "hsl(" + Math.random() * 360 + ",100%,50%)";
})
.attr("d", arc);
g.selectAll("text").data(piedata)
.enter()
.append("text")
.attr("text-anchor", "middle")
/*
.attr("x", function(d) {
var a = d.startAngle + (d.endAngle - d.startAngle) / 2 - Math.PI / 2;
d.cx = Math.cos(a) * (radius - 75);
return d.x = Math.cos(a) * (radius - 20);
})
.attr("y", function(d) {
var a = d.startAngle + (d.endAngle - d.startAngle) / 2 - Math.PI / 2;
d.cy = Math.sin(a) * (radius - 75);
return d.y = Math.sin(a) * (radius - 20);
})
*/
.attr("transform", function(d){
var pos = outerArc.centroid(d);
pos[0] = radius * (midAngle(d) < Math.PI ? 1 : -1);
return "translate("+ pos +")";
})
.text(function(d) {
return d.data.letter;
});
function midAngle(d) {
return d.startAngle + (d.endAngle - d.startAngle) / 2;
}
var polyline = g.selectAll("polyline")
.data(piedata, function(d) {
return d.data.letter
})
.enter()
.append("polyline")
.attr("points", function(d) {
var pos = outerArc.centroid(d);
pos[0] = radius * 0.95 * (midAngle(d) < Math.PI ? 1 : -1);
return [arc.centroid(d), outerArc.centroid(d), pos];
})
.style("fill", "none")
.style("stroke", "black")
.style("stroke-width", "2px");
//});
</script>
</body>
</html>