[OpenLayers-Dev] Problem with cluster strategy

Jerome Freyre jerome.freyre at hispeed.ch
Wed Nov 26 09:02:03 EST 2008

Hi everybody,

In my project, I currently use the cluster strategy.

In the example

we use a little formula in the context to define the radius :
Math.min(feature.attributes.count, 7) + 3;

Personnally, I am not sure that it is the right way to define the radius
size of the cluster.

Normally, the radius should be defined by the "max value of all cluster" and
the "max radius we autorize"!?

Personally, I add a function in the Cluster.js file which is called before
the this.layer.addFeatures(clusters) in the cluster function :

    getBiggestClusterValue: function(clusters) {
      if (this.maxVal == -1) {
        if(clusters) {
          for(var i=0; i<clusters.length; ++i) {
              if (clusters[i].attributes.count > this.maxVal)
                this.maxVal =
        return this.maxVal;
      return this.maxVal;      

And in the context, I use this formula to determine the radius

var maxClustersValue = parseInt(clusterStrategy.maxVal);
var maxRadius = 18;
var currentClusterValue = feature.attributes.nbOfSpams;
var radius = Math.ceil(currentClusterValue * (maxRadius /
return Math.max(2,radius);

Is my reflexion correct? 

Thanks all,

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