Error: attribute d: Expected number, "MNaN,NaNLNaN,NaN"

Question

I'm tring to create a multi-line chart using D3.js v4. I'm using this example: https://bl.ocks.org/mbostock/3884955. Sample csv Data: ``` storageSystem,poolId,availableVolumeCapacity,date system01,0,18031398,20170413 system01,1,15626268,20170413 system01,2,61256286,20170413 system01,3,119514990,20170413 system02,0,15046668,20170413 system02,1,12486558,20170413 system02,2,12303396,20170413 system03,0,35171335,20170413 system03,1,17263722,20170413 system01,0,18031387,20170414 system01,1,15626257,20170414 system01,2,61256275,20170414 system01,3,119514989,20170414 system02,0,15046657,20170414 system02,1,12486547,20170414 system02,2,12303385,20170414 system03,0,35171324,20170414 system03,1,17263711,20170414 ``` Data Object: ``` 0: Object color: "#8c564b" key: "system03" values: Array(2) 0: Object key: "0" values: Array(23) 0: Object availableVolumeCapacity: 35171335 date: Thu Apr 13 2017 00:00:00 GMT+0000 (Coordinated Universal Time) poolId: "0" storageSystem: "system03" 1: Object key: "1"…

Accepted Answer

The root of your problem is that the value `d` in your anonymous function passed to `dataNest.forEach` still contains one level of nesting but you are using it as if it doesn't have any nesting. Your code fails because it is looking for `date` and `availableVolumeCapacity` properties on an object that only has `key` and `values` properties.

There are ultimately two approaches to fix this:

Use a single key function which combines both the storage system and pool ID. This reduces the nesting to only one level:

```
var dataNest = d3.nest()
    .key(function(d) { return d.storageSystem + " " + d.poolId; })
    .entries(data);
```

Use two nested calls to `forEach`:

```
dataNest.forEach(function(d2,i2) {
    d2.forEach(function (d,i) {
        svg.append("path")
        // .... rest of inner function omitted
    });
});
```

You will need to go through all uses of `d` (in particular `d.key`) and `i` within the inner function (whose body I omitted for brevity) to see whether you need to incorporate `d2` and `i2`. For example, perhaps you want to use `d2.key + " " + d.key` instead of `d.key`.

Error: <path> attribute d: Expected number, "MNaN,NaNLNaN,NaN"

Solution

Problem