Derive variable labels from column names name<sep>label

Splits each column name at the first occurrence of sep, renames the column to the part before sep (the name, trimmed of surrounding whitespace), and assigns the part after sep as a "label" attribute on the column. The label attribute follows the haven convention also used by labelled::var_label(), so labelled-aware tooling (labelled, haven, varlist(), code_book(), ...) reads it transparently. Splitting at the first sep means the label itself may contain the separator.

Usage

label_from_names(df, sep = ". ")

Arguments

df: A data.frame or tibble with column names of the form "name<sep>label" (e.g. "code. question text").
sep: Character string used as separator between name and label. Default ". " (LimeSurvey's default); any literal string can be used. Matched as a fixed string, so regex metacharacters such as . or | carry no special meaning.

Value

An object of the same class as df – a base data.frame if df was a base data.frame, a tbl_df if df was a tibble. The output has column names equal to the trimmed names (before sep) and, for every column whose original name contained sep, a "label" attribute equal to the label (after sep). Columns whose name does not contain sep are passed through unchanged with no label attached.

Details

This is especially useful for LimeSurvey CSV exports when using Export results -> Export format: CSV -> Headings: Question code & question text, where column names look like "code. question text". The default separator is ". " to match that export.

LimeSurvey question codes (the part before sep) are restricted to alphanumeric characters, must start with a letter, and cannot contain spaces or special characters. The column name therefore needs to encode both the code and the question text, separated by a literal string – there is no way to recover a label from a code alone. If your export uses Headings: Question code (codes only), re-export with Headings: Question code & question text (which inserts the default ". " separator) before calling this function.

Errors

The function raises an actionable error – rather than letting the downstream constructor raise a cryptic one – when the split produces:

duplicate column names (two original names share the same prefix before sep); or
an empty column name (the original name starts with sep and has nothing before it).

Examples

# LimeSurvey-style column names (default sep = ". ").
df <- data.frame(
  "age. Age of respondent" = c(25, 30),
  "score. Total score. Manually computed." = c(12, 14),
  check.names = FALSE
)
out <- label_from_names(df)
attr(out$age, "label")
#> [1] "Age of respondent"
attr(out$score, "label")
#> [1] "Total score. Manually computed."

# Custom separator.
df2 <- data.frame(
  "id|Identifier" = 1:3,
  "score|Total score" = c(10, 20, 30),
  check.names = FALSE
)
out2 <- label_from_names(df2, sep = "|")

Derive variable labels from column names `name<sep>label`