title: D3.js d3.max undefined
body: <p>this is my first question and I´m completely new to the wonderful d3.js.
  I try to make a choropleth map out of a geojson file with 12 objects and a lot of properties. </p>
  
  <p>I want to calculate the domain for the colorscale (quantize) by d3.min and d3.max, but something must be wrong. The values of min and max are still undefined(if I believe my webinspektor).
  With Numbers in the domain tags all works fine.</p>
  
  <p>I hope someone can help me. Thanks for every answer.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>d3.json("IKSK_LK_Goe_31463.json", function (collection) {
  
  
  
  
                  overlay.afterAdd = function () {                    // Add the container when the overlay is added to the map.
  
  
                      color.domain([
                              //1,30
                              d3.min(collection, function(d) {return d.features.properties.EINWOHNER;}),
                              d3.max(collection, function(d) {return d.features.properties.EINWOHNER;})
                              ]); 
                              console.log(d3.max(collection, function(d) {return d.features.properties.EINWOHNER;}));
  </code></pre>