I have a very similar task as D3.js nesting and rollup at same time and solution provided by @altocumulus for d3.js v3 works perfectly fine for me (tested). However, I am using d3.js v4 across my website and I am having difficulties replicating the same approach with v4 - I am not getting the same results. Perhaps, because I don't understand the sumChildren function. Please feel free to provide a better or different approach on how to restructure the loaded csv file as json with subtotals at every node level using d3.js v4. In my case, I need to have Population at the Country, State and the City levels.
Disclaimer: I have been using SO for many years and in most of the cases I got my answers from questions posted by other people, but this is my first question. In addition to this I am noob in d3.js
population.csv:
Country,State,City,Population
"USA","California","Los Angeles",18500000
"USA","California","San Diego",1356000
"USA","California","San Francisco",837442
"USA","Texas","Austin",885400
"USA","Texas","Dallas",1258000
"USA","Texas","Houston",2196000
index.html:
<!DOCTYPE html>
<html>
<head>
<title> Test D3.js</title>
</head>
<!-- <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.17/d3.min.js"></script>
-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.4.0/d3.min.js"></script>
<body>
<script>
d3.csv("population.csv", function(error, data) {
if (error) throw error;
var nested = d3.nest()
.key(function(d) { return d.Country; })
.key(function(d) { return d.State; })
.rollup(function(cities) {
return cities.map(function(c) {
return {"City": c.City, "Population": +c.Population };
});
})
.entries(data);
// Recursively sum up children's values
function sumChildren(node) {
node.Population = node.values.reduce(function(r, v) {
return r + (v.values ? sumChildren(v) : v.Population);
},0);
return node.Population;
}
// Loop through all top level nodes in nested data,
// i.e. for all countries.
nested.forEach(function(node) {
sumChildren(node);
});
// Output. Nothing of interest below this line.
d3.select("body").append("div")
.style("font-family", "monospace")
.style("white-space", "pre")
.text(JSON.stringify(nested,null,2));
});
</script>
</body>
</html>
Results:
[
{
"key": "USA",
"values": [
{
"key": "California",
"value": [
{
"City": "Los Angeles",
"Population": 18500000
},
{
"City": "San Diego",
"Population": 1356000
},
{
"City": "San Francisco",
"Population": 837442
}
]
},
{
"key": "Texas",
"value": [
{
"City": "Austin",
"Population": 885400
},
{
"City": "Dallas",
"Population": 1258000
},
{
"City": "Houston",
"Population": 2196000
}
]
}
],
"Population": null
}
]
Desired Results:
[
{
"key": "USA",
"values": [
{
"key": "California",
"values": [
{
"City": "Los Angeles",
"Population": 18500000
},
{
"City": "San Diego",
"Population": 1356000
},
{
"City": "San Francisco",
"Population": 837442
}
],
"Population": 20693442
},
{
"key": "Texas",
"values": [
{
"City": "Austin",
"Population": 885400
},
{
"City": "Dallas",
"Population": 1258000
},
{
"City": "Houston",
"Population": 2196000
}
],
"Population": 4339400
}
],
"Population": 25032842
}
]
The v4 changelog tells us that
When used in conjunction with nest.rollup, nest.entries now returns {key, value} objects for the leaf entries, instead of {key, values}.
It is this little renaming from values to value within the leaf nodes which eventually breaks the code. Changing the helper function accordingly should get you back on track:
// Recursively sum up children's values
function sumChildren(node) {
if (node.value) {
node.values = node.value; // Ensure, leaf nodes will also have a values array
delete node.value; // ...instead of a single value
}
node.Population = node.values.reduce(function(r, v) {
return r + (v.value? sumChildren(v) : v.Population);
},0);
return node.Population;
}
来源：https://stackoverflow.com/questions/40878072/d3-js-nesting-and-rollup-at-the-same-time-in-v4