Support natural sorting of keys. about d3-collection

[mbostock]

Keys are always coerced to strings, so this is the expected behavior. Per the documentation for nest.key, emphasis added:

The key function will be invoked for each element in the input array and must return a string identifier to assign the element to its group.

Any return value that is not a string is coerced to a string.

[gunn]

Excellent response time.
I understand that it's expected and not a bug. It seems like it leaves sortKeys not very useful if it can't sort numbers though. Surely this will be a common problem?

[mbostock]

You can either use a string that sorts lexicographically in the desired order (for example, formatting your dates appropriately with d3-time-format), or you can coerce back to a number in your comparator function. For example, assuming that d.date is a Date object and you want to group by unique dates (milliseconds):

const nest = d3.nest()
    .key(d => +d.date)
    .sortKeys((a, b) => a - b)
    .entries(data);

[gunn]

Okay workarounds for now then. I suppose this might change in the future with #11. Thank you Mike.

[mbostock]

Exactly.