It is possible to color the clustered icons based on the properties of the icons clustered together. The easiest method might be to use htmlwidgets and call a javascript function on map rendering.
However, before getting to the htmlwidget, you need to set a clusterId for your clustered layer:
addAwesomeMarkers(clusterId = "cluster" ...
Now we can find this layer when in the htmlwidget:
function(el, x) {
map = this; // the map object
var cluster = map.layerManager.getLayer('cluster','cluster'); // the cluster layer
Within the cluster layer, we want to create a function for the icon property iconCreateFunction:
cluster.options.iconCreateFunction = function(d) {
// generate icon
}
This function should:
- go through all the child markers represented by the clustered marker,
- identify the highest rank of those child markers
- return an appropriate icon
1. Iterating through child markers
For number one, and building on the above, we can iterate through each child marker with:
cluster.options.iconCreateFunction = function(c) {
var markers = c.getAllChildMarkers();
markers.forEach(function(m) {
// do something for each marker
})
}
I'm using c to represent a cluster, m to represent each individual child marker
2. Getting the Highest Ranked Marker
The primary challenge in the list is identifying the highest rank of the child icons - as the data is not bound to the icons we are limited in options. Assuming that the color of the icons corresponds to the color code of the item in the dataframe, I will use the color of the icon to determine its priority/rank. After determining the highest ranking child, I will color the cluster based on that child's rank.
I will color the cluster as follows (as I believe this is your intended result):
- red if any child icons are red,
- orange if none are red but there are some orange children, and
- green if there is no orange or red children.
To get the color, I need to access the proper property. The color (fill) of an (awesome) marker resides at:
marker.options.icon.options.markerColor
To compare colors, I'll use an object to represent each color's rank, this will allow for a simple comparison of color:
var priority = {
'green':0,
'orange':1,
'red':2
}
This allows:
cluster.options.iconCreateFunction = function(c) {
var markers = c.getAllChildMarkers();
var priority = {
'green': 0,
'orange': 1,
'red': 2
};
var highestRank = 0; // defaults to the lowest level to start
markers.forEach(function(m) {
var color = m.options.icon.options.markerColor;
// check each marker to see if it is the highest value
if(priority[color] > highestRank) {
highestRank = priority[color];
}
})
}
3. Returning an Icon
Now that we have a value representing a color, we can return an icon. Leaflet clustered icons have limited styling options. They use L.divIcon(), which limits options somewhat. When combined with css styles for clustered labels, they create the familiar circle with green, yellow, and orange colors.
These default styles have the following css classes:
.marker-cluster-small // green
.marker-cluster-medium // yellow
.marker-cluster-large // orange
If we are happy with just using these classes, we can style the clustered polygons with minimal effort:
var styles = [
'marker-cluster-small', // green
'marker-cluster-medium', // yellow
'marker-cluster-large' // orange
]
var style = styles[highestRank];
var count = markers.length;
return L.divIcon({ html: '<div><span>'+count+'</span></div>', className: 'marker-cluster ' + style, iconSize: new L.Point(40, 40) });
The whole widget therefore looks like:
function(el,x) {
map = this;
var cluster = map.layerManager.getLayer('cluster','cluster');
cluster.options.iconCreateFunction = function(c) {
var markers = c.getAllChildMarkers();
var priority = {
'green': 0,
'orange': 1,
'red': 2
};
var highestRank = 0; // defaults to the lowest level to start
markers.forEach(function(m) {
var color = m.options.icon.options.markerColor;
// check each marker to see if it is the highest value
if(priority[color] > highestRank) {
highestRank = priority[color];
}
})
var styles = [
'marker-cluster-small', // green
'marker-cluster-medium', // yellow
'marker-cluster-large' // orange
]
var style = styles[highestRank];
var count = markers.length;
return L.divIcon({ html: '<div><span>'+count+'</span></div>', className: 'marker-cluster ' + style, iconSize: new L.Point(40, 40) });
}
}
Refining the Icons
Changing Colors
You probably want to have the high priority icons show up red. This can be done, but you need to add a css style to your map.
One way to do this at the same time as changing the icon function above is to append a style to the page with javascript in your widget. You need to make two styles, one for the div holding the icon, and one for the icon, you can do both at once:
var style = document.createElement('style');
style.type = 'text/css';
style.innerHTML = '.red, .red div { background-color: rgba(255,0,0,0.6); }'; // set both at the same time
document.getElementsByTagName('head')[0].appendChild(style);
(from https://stackoverflow.com/a/1720483/7106086)
Don't forget to update what classes you are using in the styles array:
var styles = [
'marker-cluster-small', // green
'marker-cluster-medium', // yellow
'red' // red
]
Showing More Information in the Icon
You aren't limited to a number in the icon, you could show 1-3-5 , representing one high priority, three medium etc. You just need to keep track of how many child icons of each priority are in each cluster:
var children = [0,0,0];
markers.forEach(function(m) {
var color = m.options.icon.options.markerColor;
children[priority[color]]++; // increment the appropriate value in the children array.
...
Then show it with:
return L.divIcon({ html: '<div><span>'+children.reverse()+'</span>...
Givings something like:
Test Example
This should be copy and pastable to show everything except the additional text in the icon (using the code in these documentation examples as a base):
library(leaflet)
# first 20 quakes
df.20 <- quakes[1:50,]
getColor <- function(quakes) {
sapply(quakes$mag, function(mag) {
if(mag <= 4) {
"green"
} else if(mag <= 5) {
"orange"
} else {
"red"
} })
}
icons <- awesomeIcons(
icon = 'ios-close',
iconColor = 'black',
library = 'ion',
markerColor = getColor(df.20)
)
leaflet(df.20) %>% addTiles() %>%
addAwesomeMarkers(~long, ~lat, icon=icons, label=~as.character(mag), clusterOptions = markerClusterOptions(), group = "clustered", clusterId = "cluster") %>%
htmlwidgets::onRender("function(el,x) {
map = this;
var style = document.createElement('style');
style.type = 'text/css';
style.innerHTML = '.red, .red div { background-color: rgba(255,0,0,0.6); }'; // set both at the same time
document.getElementsByTagName('head')[0].appendChild(style);
var cluster = map.layerManager.getLayer('cluster','cluster');
cluster.options.iconCreateFunction = function(c) {
var markers = c.getAllChildMarkers();
var priority = {
'green': 0,
'orange': 1,
'red': 2
};
var highestRank = 0; // defaults to the lowest level to start
markers.forEach(function(m) {
var color = m.options.icon.options.markerColor;
// check each marker to see if it is the highest value
if(priority[color] > highestRank) {
highestRank = priority[color];
}
})
var styles = [
'marker-cluster-small', // green
'marker-cluster-large', // orange
'red' // red
]
var style = styles[highestRank];
var count = markers.length;
return L.divIcon({ html: '<div><span>'+count+'</span></div>', className: 'marker-cluster ' + style, iconSize: new L.Point(40, 40) });
}
}")
