d3：更新数据集而不更新DOM

Question

I want to create a list using D3 using the following data:

var dataSet = [
    { label: 'a', value: 10},
    { label: 'b', value: 20},
    { label: 'c', value: 30},
    { label: 'd', value: 40}
];

var circle = svg.selectAll('circle')
    .data(dataSet)
    .enter()
    .append('circle')
    .attr({
        r:function(d){ return d.value },
        cx:function(d, i){ return i * 100 + 50 },
        cy:50,
        fill: 'red'
    });

Which works. Now after some time, I change the data

dataSet[0].value = 40;
dataSet[1].value = 30;
dataSet[2].value = 20;
dataSet[3].value = 10;

and I would like to draw the list again:

setTimeout(function () {
    var circle = svg.selectAll('circle')
      .data(dataSet, function (d) {
          return d.label;   
      })
     .sort(function (a,b){ return d3.ascending(a.value, b.value);})
     .enter()
     .append('circle')
     .attr({
        r:function(d){ return d.value },
        cx:function(d, i){ return i * 100 + 50 },
        cy:50,
        fill: 'red'
     });
},1000);

DEMO

However, this list is not really updated. Any suggestions how to fix this ?

Answer 1

you need to clear svg.html(''); in setTimeout
DEMO

Answer 2

This can be accomplished by removing the existing circles first by calling:

svg.selectAll('circle').remove()

and then going through adding them again with different data set. I updated your fiddle http://jsfiddle.net/Q5Jag/1183/

Hope this helps.

Here is same fiddle with some enter and exit animations http://jsfiddle.net/Q5Jag/1184/

Answer 3

The problem is that you're handling only the enter selection, which will be empty on update -- you need to handle the update selection:

svg.selectAll('circle')
.data(dataSet, function (d) {
    return d.label;   
})
.sort(function (a,b){ return d3.ascending(a.value, b.value);})
.transition()
.attr({
    r:function(d){ return d.value },
    cx:function(d, i){ return i * 100 + 50 },
    cy:50,
    fill: 'red'
});

Updated fiddle here . For more information on the different selections, have a look at this tutorial .