D3 js get a d3.max from an object that contains a specific key value

问题

I have the following dataset and am trying to get the d3.max to specify a domain for a scale, but want the d3.max value only from objects that have the key enabled=true. How can this be achieved?

[{
    "key": "name1",
    "enabled": "true",
    "values": [{
        "date": "2016-09-13T02:11:44Z",
        "value": "100",
    }, {
        "date": "2016-09-13T02:11:44Z",
        "value": "200",
    }]
}, {
    "key": "name2",
    "enabled": "false",
    "values": [{
        "date": "2016-09-13T02:11:44Z",
        "value": "400",
    }, {
        "date": "2016-09-13T02:11:44Z",
        "value": "500",
    }]
}]

I think I am supposed to use a key somehow, but haven't been able to do it. Can someone point me to the right direction? This is what I have so far...

d3.max(dataset, function(c) { return d3.max(c.values, function(d) { return d.value; }); })

回答1:

If you want it in one line:

var max = d3.max(data.filter(d => d.enabled === "true"), e => d3.max(e.values, f => f.value));

Or, without the arrow functions:

var max = d3.max(data.filter(function(d) {
    return d.enabled === "true";
}), function(e) {
    return d3.max(e.values, function(f) {
        return f.value;
    });
});

Here is a demo:

var data = [{
  "key": "name1",
  "enabled": "true",
  "values": [{
    "date": "2016-09-13T02:11:44Z",
    "value": "100",
  }, {
    "date": "2016-09-13T02:11:44Z",
    "value": "200",
  }]
}, {
  "key": "name2",
  "enabled": "false",
  "values": [{
    "date": "2016-09-13T02:11:44Z",
    "value": "400",
  }, {
    "date": "2016-09-13T02:11:44Z",
    "value": "500",
  }]
}];

var max = d3.max(data.filter(d => d.enabled === "true"), e => d3.max(e.values, f => f.value));

console.log(max);

<script src="https://d3js.org/d3.v4.min.js"></script>

It accepts more than one object with enabled: "true", check this second demo, I put another object in your data array:

var data = [{
  "key": "name1",
  "enabled": "true",
  "values": [{
    "date": "2016-09-13T02:11:44Z",
    "value": "100",
  }, {
    "date": "2016-09-13T02:11:44Z",
    "value": "200",
  }]
}, {
  "key": "name2",
  "enabled": "false",
  "values": [{
    "date": "2016-09-13T02:11:44Z",
    "value": "400",
  }, {
    "date": "2016-09-13T02:11:44Z",
    "value": "500",
  }]
},{
  "key": "name1",
  "enabled": "true",
  "values": [{
    "date": "2016-09-13T02:11:44Z",
    "value": "800",
  }, {
    "date": "2016-09-13T02:11:44Z",
    "value": "200",
  }]
}];

var max = d3.max(data.filter(d => d.enabled === "true"), e => d3.max(e.values, f => f.value));

console.log(max);

<script src="https://d3js.org/d3.v4.min.js"></script>

来源：https://stackoverflow.com/questions/42930052/d3-js-get-a-d3-max-from-an-object-that-contains-a-specific-key-value

标签

javascript

d3.js

dataset