Converts a data.frame or matrix in wide format (with an ID column and
repeated‐measure columns named <variable>_<time>, e.g. V1_1, V1_2)
into long format. The resulting data has columns ID, any between‐subject
factors, time, and one column per measure.
Arguments
- data
A data.frame or matrix in wide format. If a matrix is
provided, it will be coerced to a data.frame. Must have at least two columns
matching the regex "<var>_<time>".
Value
A data.frame in long format with columns ID, any between‐subject
factors (if present), time (integer), and one column per measure.
