传单中两个组的自定义标记集群

Question

假设 data.frame 的“group”列具有唯一值“group1”和“group2”。在传单中，我们可以为这些组分配带有

ColorFactor()

的颜色。我们还可以使用最少的 CSS 来更改标记簇颜色。

我们如何为每个组的 markerClusters 分配不同的颜色？换句话说，我希望“group1”内的点的所有标记簇都为“海军蓝”，并且“group2”内的点的所有标记簇在所有缩放级别上都为“红色”，甚至到各个点。

在 Rmd 文件中：

---
output: html_document
---

<style>
.marker-cluster-small {
background-color: green;
}
.marker-cluster-small div {
background-color: green;
}
.marker-cluster-medium {
background-color: green;
}
.marker-cluster-medium div {
background-color: green;
}
.marker-cluster-large {
background-color: green;
}
.marker-cluster-large div {
background-color: green;
}
</style>

```{r}
library(leaflet)
library(magrittr)
quakes$group <- sample(c("group1", "group2"), 1000, replace = TRUE)
pal_group <- colorFactor(c("navy", "red"), c("group1", "group2"))

leaflet() %>% 
  addTiles() %>% 
  addCircleMarkers(
    lng = quakes$long, 
    lat = quakes$lat, 
    clusterOptions = markerClusterOptions(),
    color = pal_group(quakes$group)
  )

Answer 1

似乎您可能对这个答案感兴趣：防止多个标记集群组图标在 Leaflet 中重叠

使用 2 个单独的 MarkerClusterGroup 可能不合适，通常是在某些点位于附近位置但针对不同组的情况下。在这种情况下，Leaflet.markercluster 可能会在同一位置显示 2 个独立的簇，彼此重叠（这正是我们首先要通过使用聚类来避免的情况）。

为了仍然显示集群，提示每个类别的子标记数量，我们必须自定义集群图标。链接的答案提出了这样的自定义功能：

function customClusterIcon(cluster) {
  // Count number of markers from each category.
  var markers = cluster.getAllChildMarkers();
  var cat1count = 0;
  var cat2count = 0;
  for (var marker of markers) {
    var category = marker.options.category;
    if (category && category === 'cat2') {
      cat2count += 1;
    } else {
      cat1count += 1;
    }
  }
  // Generate the cluster icon depending on presence of Markers from different categories.
  if (cat2count === 0) {
    return L.divIcon({
      html: cat1count,
      className: 'cat1cluster cluster',
      iconSize: [20, 20]
    });
  } else if (cat1count === 0) {
    return L.divIcon({
      html: cat2count,
      className: 'cat2cluster cluster',
      iconSize: [20, 20]
    });
  } else {
    return L.divIcon({
      html: `
        <div class="cat1cluster cluster">${cat1count}</div>
        <div class="cat2cluster cluster">${cat2count}</div>
      `,
      className: '',
      iconSize: [45, 20]
    });
  }
}

var paris = [48.86, 2.35];
var parisLeft = [48.86, 2.25];
var parisRight = [48.86, 2.45];
var map = L.map('map', {
  maxZoom: 18
}).setView(paris, 11);

var mcg = L.markerClusterGroup({
  iconCreateFunction: customClusterIcon
}).addTo(map);
var category1 = L.layerGroup();
var category2 = L.layerGroup();

var cat2style = {
  color: 'red',
  category: 'cat2'
};

var markerA = L.circleMarker(paris).addTo(category1);
var markerB = L.circleMarker(paris).addTo(category1);
var markerC = L.circleMarker(paris, cat2style).addTo(category2);
var markerD = L.circleMarker(paris, cat2style).addTo(category2);

var markerE = L.circleMarker(parisLeft).addTo(category1);
var markerF = L.circleMarker(parisLeft).addTo(category1);

var markerG = L.circleMarker(parisRight, cat2style).addTo(category2);
var markerH = L.circleMarker(parisRight, cat2style).addTo(category2);

mcg.addLayers([category1, category2]);


L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
  attribution: '&copy; <a href="http://osm.org/copyright">OpenStreetMap</a> contributors'
}).addTo(map);

html,
body,
#map {
  height: 100%;
  margin: 0;
}

.cat1cluster {
  background-color: #3388ff;
}

.cat2cluster {
  background-color: red;
}

.cluster {
  width: 20px;
  height: 20px;
  display: inline-block;
  text-align: center;
}

<!-- Leaflet assets -->
<link rel="stylesheet" href="https://unpkg.com/[email protected]/dist/leaflet.css" integrity="sha512-puBpdR0798OZvTTbP4A8Ix/l+A4dHDD0DGqYW6RQ+9jxkRFclaxxQb/SJAWZfWAkuyeQUytO7+7N4QKrDh+drA==" crossorigin="" />
<script src="https://unpkg.com/[email protected]/dist/leaflet-src.js" integrity="sha512-+ZaXMZ7sjFMiCigvm8WjllFy6g3aou3+GZngAtugLzrmPFKFK7yjSri0XnElvCTu/PrifAYQuxZTybAEkA8VOA==" crossorigin=""></script>

<!-- Leaflet.markercluster assets -->
<link rel="stylesheet" href="https://unpkg.com/[email protected]/dist/MarkerCluster.css">
<link rel="stylesheet" href="https://unpkg.com/[email protected]/dist/MarkerCluster.Default.css">
<script src="https://unpkg.com/[email protected]/dist/leaflet.markercluster-src.js"></script>


<div id="map"></div>