Type Alias: ColumnType

ColumnType = "number" | "string" | "boolean" | "date"

What a declared column holds.

word	what a value must be
`number`	a JavaScript number that is FINITE — `NaN` and the infinities are a number that means "no number", and a chart handed one draws nothing
`string`	a JavaScript string, including the empty one (emptiness is meaning, and meaning is above this check's ceiling)
`boolean`	`true` or `false` — never `'true'`, never `0`, never `1`
`date`	a valid `Date` instance, or a string `Date.parse` accepts (an epoch NUMBER is a `number`; say so and the axis picker stops guessing)

ColumnType