Parse variableStart field to extract raw variable name

This function parses the variableStart field from variable_details metadata and extracts the raw variable name for a specific database/cycle. It supports recodeflow-standard formats: database-prefixed ("database::varname"), bracket ("[varname]"), mixed, and plain formats.

Usage

parse_variable_start(variable_start, cycle)

Arguments

variable_start

Character string from variableStart field. Can contain multiple database specifications separated by commas (e.g., "cycle1::age, cycle2::AGE").

cycle

Character string specifying the database/cycle to extract (e.g., "cycle1", "cchs2001").

Value

Character string with the raw variable name, or NULL if not found.

Details

The function implements recodeflow-standard parsing strategies:

1. Database-prefixed format: "database::varname" - for database-specific names

2. Bracket format (whole string): "[varname]" - for database-agnostic names

3. Bracket format (segment): "database1::var1, [var2]" - [var2] is DEFAULT for other databases

4. Plain format: "varname" - uses value as-is

Important: [variable] represents the DEFAULT for all databases not explicitly referenced with database:: notation. This reduces repetition when only one or a few databases use different variable names.

For DerivedVar format, returns NULL (requires custom derivation logic).

See also

Other parsing-utilities: parse_range_notation()

Examples

# Database-prefixed format
parse_variable_start("cycle1::height, cycle2::HEIGHT", "cycle1")
#> [1] "height"
# Returns: "height"

# Bracket format (database-agnostic)
parse_variable_start("[gen_015]", "cycle1")
#> [1] "gen_015"
# Returns: "gen_015"

# Mixed format - [variable] is DEFAULT for databases not explicitly listed
parse_variable_start("cycle1::amsdmva1, [ammdmva1]", "cycle2")
#> [1] "ammdmva1"
# Returns: "ammdmva1" (uses default for cycle2)

# Plain format
parse_variable_start("bmi", "cycle1")
#> [1] "bmi"
# Returns: "bmi"

# No match for specified database
parse_variable_start("cycle2::age", "cycle1")
#> NULL
# Returns: NULL