I think in this case the only way you are going to get the correct result is to create the table with a schema, rather than rely on type inference. There's only so far down the rabbit hole we can go...

The json is coming out as 1.000 though. I would get that if it looked like {[1, 2.5, 3.4]} etc where the first value is actually an int.

The magic is here:

https://github.com/jpmorganchase/perspective/blob/828a2614e638bd277863495d3f69f7c2f1586a79/packages/perspective/src/js/perspective.js#L37-L62

It tries to guess the types - but it isn't always going to work (especially in js, where we lack the distinction between an int and a float).

closing, the solution is really to use a schema