d3 selectAll: count results

Question

How do I count how many nodes were matched by a selectAll? (without joined data)

Or if there's data, how to count the data from the selection? (suppose I've set it with "data(function...)" so I don't know the length in advance)

Answer 1

Just use d3.selectAll(data).size().Hope this example help you:

 var matrix = [    [11975,  5871, 8916, 2868],    [ 1951, 10048, 2060, 6171],    [ 8010, 16145, 8090, 8045],    [ 1013,   990,  940, 6907]  ];   var tr = d3.select("body").append("table").selectAll("tr")             .data(matrix)             .enter().append("tr");   var td = tr.selectAll("td")           .data(function(d) { return d; })           .enter().append("td")           .text(function(d) { return d; });  var tdSize=tr.selectAll("td").size(); 

Complete jsfiddle here.

Answer 2

One way I have done this previously is to pass that information into the data function by making a new object.

 .data(function(d) {               return d.Objects.map(function(obj) {          return {              Object: obj,              TotalObjects: d.Objects.length          }    }); 

Then in your update portions you use Object and still have the count available.

.attr("x", function(d) {      return d.Object.X;  })  .attr("y", function(d) {      return d.TotalObjects;  })