# `Macaw.Data.Operations.Transforms.M4`
[🔗](https://github.com/dcoai/macaw_data/blob/v0.5.3/lib/macaw/data/operations/transforms/time.ex#L131)

`m4` (spec/04 §4.5): per pixel column the first, last, least and greatest rows
(`Macaw.Data.Reduce.m4/3`), deduplicated in order, so every column's extremes survive.
`width` is frame-bound. A reducer (spec/04 §7).

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*Consult [api-reference.md](api-reference.md) for complete listing*