Extract Person-Level Covariates from IRW Long-Format Data

Reduces IRW long-format data to one row per id, keeping the columns that describe the person rather than the response. Optionally aligns those rows to the row order of a wide response matrix, which is what most psychometric packages need when a grouping variable is passed alongside a response matrix.

Usage

irw_covariates(df, cols = NULL, align = NULL)

Arguments

df

A data frame in IRW long format, containing an id column.

cols

Character vector of person-level columns to extract. Defaults to NULL, meaning detect them automatically as described above.

align

Optional. A data frame with an id column (such as the result of irw_long2resp()), a matrix with id rownames, or a vector of ids. The returned rows are put in this order, one row per element, so the result lines up with the rows of a wide response matrix.

Value

A data frame with one row per id and columns id followed by the person-level covariates. When align is supplied, rows follow that order and ids not present in df yield NA rows.

Details

irw_long2resp() keeps only id, item, and the response column, so person-level covariates are dropped and the row order of its result is not sorted. Aligning a covariate to that result by hand requires a match() on id, and getting it wrong silently misassigns people to groups. Passing the wide result as align does that match for you.

When cols is NULL, the person-level columns are detected automatically: every column other than id and the response-level columns (item, resp, rater, rt, text, date, source_table) that takes exactly one value within every id. A column with a value for some of a person's rows and NA for others counts as varying and is not selected. Note that wave is treated as person-level only when each person appears in a single wave.

See also

irw_long2resp

Examples

df <- data.frame(
  id = c(1, 1, 2, 2),
  item = c("i1", "i2", "i1", "i2"),
  resp = c(1, 0, 1, 1),
  cov_group = c("A", "A", "B", "B"),
  stringsAsFactors = FALSE
)
irw_covariates(df)
#>   id cov_group
#> 1  1         A
#> 2  2         B

# Aligned to the row order of a wide response matrix
wide <- irw_long2resp(df, id_density_threshold = NULL)
irw_covariates(df, align = wide)
#>   id cov_group
#> 1  1         A
#> 2  2         B