Scale Missing Values
Missing and invalid values
Point encodings can provide an unknown fallback inside their scale options:
program.encodeX({
field: "value",
scale: { domain: [0, 100], unknown: 20 }
});
The fallback is used for a missing or field-type-invalid input. For ordinal
point position or appearance, it also handles a value outside an explicit
domain. It never becomes a domain member. Output validation follows the
channel: position uses a finite coordinate, color a non-empty string, size a
non-negative area, opacity a value from 0 to 1, and shape one supported
point shape.
This policy is intentionally limited to row-owned point items. A missing value
inside a line/area path, bar aggregate, rule, xOffset group, or stroke-dash
series could change item topology; those consumers reject unknown until they
have a separate topology-safe policy. A direct unattached scale stores its
fallback and defers channel validation until attachment. Set
unknown: undefined with editScale to remove an existing fallback.