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Default metadata structure

Source: R/metadata_default.R
list_default_metadata.Rd

Returns the default metadata tree. Fields are grouped into categories (#118) — recording, time, space, variables, structure — with spec_version at the top level. Access stays flat: a field is read with get_metadata(data, "sampling_rate") and written with set_metadata(data, sampling_rate = 30) regardless of its category, and a category name returns the whole category.

The categories:

  • recording — provenance: source, source_version, source_format, source_sampling_rate, filename. source_sampling_rate is the rate the device recorded at, in Hz, and no processing changes it; see set_metadata() for how it is filled.

  • time — unit_time, sampling_rate (declared: the rate of the data as it is now, which resampling changes), sampling_interval (derived from the index; read it with get_sampling_interval()), start_datetime.

  • space — coordinate_system, reference_frame, handedness, axis_directions, axis_extents, unit_space, unit_angle, and euler_sequence / euler_intrinsic: the Euler convention the data's source uses, for showing and entering a quaternion orientation. The one category a class can lack: an anievent() has no spatial component, so its metadata simply has no space (#73).

  • variables — which columns play which role, as a list of roles each holding named slots: what$keys (identity), when$index + when$keys (temporal; an anievent has when$interval instead of an index), where$position (the axis-role mapping; names are roles, values are columns), event$state + event$point. The frame groups by c(what$keys, when$keys) and nothing else. These slots are reached through get_variables(), get_index() and get_axes(), never by flat name — keys appears under two roles.

  • structure — named anistructure()s, each relating the levels of one variable; see set_structure().

  • spec_version — named list of semantic version strings, one per class, versioning the full data contract independently of the package version.

Usage

list_default_metadata(class = c("anipoint", "anievent"))

Arguments

class

Which class's tree to return: "anipoint" (the default) or "anievent". An anievent's tree has no space category, and its when role carries interval = c("start", "stop") instead of an index.

Value

A named list: the categories above plus spec_version.

See also

set_metadata(), get_metadata()

Examples

names(list_default_metadata())
#> [1] "spec_version" "recording"    "time"         "space"        "variables"   
#> [6] "structure"   
names(list_default_metadata("anievent"))
#> [1] "spec_version" "recording"    "time"         "variables"    "structure"