我有一个数据集,其中包含椭圆形,更具体地说是“椭圆形包络”。我想知道是否有人能够为我提供建议,告诉我如何在D3地图上绘制它们。我已经使用Mercator投影设置好了地图。这个stackoverflow答案有一个createEllipse函数,让我接近目标,但我想确保我正确解释了数据。
我将数据中的长/短轴值插入到了函数中,并使用方位角进行旋转,这样做对吗?我也不太理解“包络”部分。每个区域中的几个椭圆如何创建单个连续形状?
任何建议都将不胜感激。
我将数据中的长/短轴值插入到了函数中,并使用方位角进行旋转,这样做对吗?我也不太理解“包络”部分。每个区域中的几个椭圆如何创建单个连续形状?
任何建议都将不胜感激。
const margin = {top:0, right:0, bottom:0, left:0},
width = 1000 - margin.left - margin.right,
height = 800 - margin.top - margin.bottom;
const svg = d3.select('body')
.append('svg')
.attr('width', '100%')
.attr('height', '100%')
.attr('viewBox', `0 0 ${width + margin.left + margin.right} ${height + margin.top + margin.bottom}`);
const chart = svg.append('g')
.attr('transform', `translate(${margin.left},${margin.top})`);
//a/b are ellipse axes, x/y is center
const createEllipse = function createEllipse(a, b, x = 0, y = 0, rotation = 0) {
let k = Math.ceil(36 * (Math.max(a/b,b/a))); // sample angles
let coords = [];
for (let i = 0; i <= k; i++) {
let angle = Math.PI*2 / k * i + rotation;
let r = a * b / Math.sqrt(a*a*Math.sin(angle)*Math.sin(angle) + b*b*Math.cos(angle)*Math.cos(angle));
coords.push(getLatLong([x,y],angle,r));
}
return { 'type':'Polygon', 'coordinates':[coords] };
}
const getLatLong = function getLatLong(center,angle,radius) {
let rEarth = 6371; // kilometers
x0 = center[0] * Math.PI / 180; // convert to radians.
y0 = center[1] * Math.PI / 180;
let y1 = Math.asin( Math.sin(y0)*Math.cos(radius/rEarth) + Math.cos(y0)*Math.sin(radius/rEarth)*Math.cos(angle) );
let x1 = x0 + Math.atan2(Math.sin(angle)*Math.sin(radius/rEarth)*Math.cos(y0), Math.cos(radius/rEarth)-Math.sin(y0)*Math.sin(y1));
y1 = y1 * 180 / Math.PI;
x1 = x1 * 180 / Math.PI;
return [x1,y1];
}
d3.json('https://media.journalism.berkeley.edu/upload/2019/11/kazakhstan.json').then((data) => {
const ellipses = [
{lat: 48.6, lng: 64.7, axis_x: 30, axis_y: 16, azimuth: 26.5, area_hectar: 0.0713, zone: 'U1'},
{lat: 48.625, lng: 64.625, axis_x: 30, axis_y: 16, azimuth: 26.5, area_hectar: 0.0713, zone: 'U1'},
{lat: 48.366, lng: 65.44166, axis_x: 50, axis_y: 30, azimuth: 40, area_hectar: 0.11775, zone: 'U2'},
{lat: 48.85, lng: 65.61666, axis_x: 20, axis_y: 22, azimuth: 29, area_hectar: 0.17584, zone: 'U3'},
{lat: 48.9333, lng: 65.8, axis_x: 22, axis_y: 22, azimuth: 28, area_hectar: 0.17584, zone: 'U3'},
{lat: 48.9166, lng: 66.05, axis_x: 50, axis_y: 20, azimuth: 38, area_hectar: 0.17584, zone: 'U3'},
{lat: 48.9166, lng: 65.68333, axis_x: 20, axis_y: 22, azimuth: 29, area_hectar: 0.17584, zone: 'U3'},
{lat: 49, lng: 65.86666, axis_x: 22, axis_y: 22, azimuth: 29, area_hectar: 0.17584, zone: 'U3'}
]
const projection = d3.geoMercator()
.fitExtent([[0,0],[width,height]], data)
const path = d3.geoPath()
.projection(projection);
chart.selectAll('path')
.data(data.features)
.enter()
.append('path')
.attr('d', path)
.attr('stroke', 'black')
.attr('strok-width', '1px')
.attr('fill', 'none');
chart.selectAll(".ellipses")
.data(ellipses.map((d) => createEllipse(d.axis_x, d.axis_y, d.lng, d.lat, d.azimuth)))
.enter()
.append('path')
.attr('d', path)
.attr('stroke', 'black')
.attr('stroke-width', '1px')
.attr('fill', 'orange');
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>
<div id="chart"></div>