d3.extent() on object keys (not values)

Question

I have an object that looks like this,

{
    "1420165140": 172.52,
    "1420254360": 63.78,
    "1420341900": 141.55,
    "1420422480": 85.8,
    "1421035920": 86.07,
    "1422506820": 118.42
}

The keys are epoch time stamps. I would like to extract the max and min dates of the keys using something like this,

var  range = d3.extent(d, function(d){ return d.key });

I've tried casting +d.key to a number from a string.

Unfortunately, all I get back is [undefined, undefined]

How can I run d3.extent on object keys?

Use [`d3.entries()`](https://github.com/mbostock/d3/wiki/Arrays#d3_entries). — Lars Kotthoff, Mar 15 '16 at 16:47
@LarsKotthoff Should be [`d3.keys()`](https://github.com/mbostock/d3/wiki/Arrays#d3_keys), right? — altocumulus, Mar 15 '16 at 20:18
@altocumulus Can use that as well -- with `d3.entries` the rest of the code (`d.key`) can remain the same. — Lars Kotthoff, Mar 15 '16 at 20:23
@LarsKotthoff Wow, good catch! I hadn't thought about that. Nice! — altocumulus, Mar 15 '16 at 20:42

score 2 · Accepted Answer · edited Mar 15 '16 at 20:43

2

You'll need to use it as

var range = d3.extent(Object.keys(d));

where d is your JSON object.

edited Mar 15 '16 at 20:43

altocumulus

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answered Mar 15 '16 at 17:02

Taran J

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d3.extent() on object keys (not values)

1 Answers1