# `Macaw.Data.Operations.Transforms.Fold` [๐Ÿ”—](https://github.com/dcoai/macaw_data/blob/v0.5.3/lib/macaw/data/operations/transforms/rows.ex#L131) `fold` (spec/04 ยง4.7): wide columns to long rows, one per input row per listed column the row has, in row then `fields` order; the row's other columns carried, the folded ones dropped by spelling; the column's name under the first name of `as`, its value under the second. A listed column the rows lack, and a `nil` reading, yield no row. --- *Consult [api-reference.md](api-reference.md) for complete listing*