Re-align metadata with a transformed data frame

Re-attach and reconcile a artoo_meta after a transformation that dropped or reshaped it: the metadata's columns are narrowed and reordered to the frame's current columns, the record count is refreshed, the keys are recomputed, and a column the metadata does not describe gets an entry synthesized from its class and attributes. The one-liner to run after a dplyr (or base) pipeline, before handing the frame to a write_*() codec.

Usage

sync_meta(x, meta = NULL)

Arguments

x

The transformed data frame. <data.frame>: required.

meta

The metadata to reconcile against. <artoo_meta> | NULL. NULL (default) uses the frame's own metadata_json attribute.

Requirement: when the transform dropped the attribute (base [ subsetting does), capture get_meta() before the pipeline and pass it here; a bare frame with no meta aborts with artoo_error_input.

Value

A <data.frame>: x re-stamped with the reconciled artoo_meta. Hand it to any write_*() codec.

Details

Why it exists. Base row subsetting (x[i, ]) drops the frame's metadata_json attribute, and many tidyverse verbs rebuild the frame. sync_meta() takes the last-known metadata (the frame's own attribute when it survived, or an explicit meta) and makes it agree with the data again, so the round trip stays lossless without hand-editing.

Examples

spec <- artoo_spec(cdisc_adam_datasets, cdisc_adam_variables, codelists = cdisc_codelists)

# ---- Example 1: re-attach after an attribute-dropping subset ----
#
# Base subsetting drops the metadata; capture it first, transform, then
# sync. The metadata narrows to the kept columns and the new row count.
adsl <- apply_spec(cdisc_adsl, spec, "ADSL", conformance = "off")
meta <- get_meta(adsl)
elderly <- adsl[adsl$AGE > 65, c("STUDYID", "USUBJID", "AGE")]
synced <- sync_meta(elderly, meta)
get_meta(synced)@dataset$records
#> [1] 46

# ---- Example 2: a derived column gains a synthesized entry ----
#
# A new column the metadata does not describe is profiled from its class,
# so the frame still writes losslessly.
adsl$AGEGR9 <- ifelse(adsl$AGE > 65, ">65", "<=65")
synced2 <- sync_meta(adsl)
#> Synthesized metadata for 1 new column: `AGEGR9`.
#> ℹ Edit the spec (or the meta) if the inferred types need refining.
get_meta(synced2)@columns$AGEGR9$dataType
#> [1] "string"