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Summary

Exposes the existing Series member slicing methods (Before, After, StartAt, EndAt, Between) as F#-style module functions, and adds matching Frame.rows* module functions for row range selection. Closes #191.

Motivation

The member methods have existed for a long time but were not available as Series.xxx pipe-able module functions, forcing users to mix member-call syntax (series.After(k)) with pipeline style in F# code. This is the gap called out in #191 ("It's irksome to mix |> and member styles at times").

New functions

Series module

Frame module

Usage

// Filter a price series to only 2024 data
let prices2024 = prices |> Series.startAt (DateTime(2024, 1, 1)) |> Series.endAt (DateTime(2024, 12, 31))
// Equivalent to:
let prices2024' = prices |> Series.between (DateTime(2024, 1, 1)) (DateTime(2024, 12, 31))

// Slice a frame to rows after a given date
let recent = df |> Frame.rowsAfter (DateTime(2024, 6, 1))

Implementation notes

• All Series functions are thin wrappers that delegate to the existing member methods — zero added logic.
• Frame functions call frame.GetSubrange(lo, hi) with the appropriate BoundaryBehavior options, consistent with how Frame.fs uses it internally.
• Added open Deedle.Indices to FrameModule.fs to bring BoundaryBehavior into scope.

Test Status

✅ All 500 tests pass (494 baseline + 6 new tests)

New tests added:

• Series.after module function matches member After
• Series.before module function matches member Before
• Series.startAt module function matches member StartAt
• Series.endAt module function matches member EndAt
• Series.between module function returns inclusive range
• Frame.rowsAfter, rowsBefore, rowsStartAt, rowsEndAt, rowsBetween work on ordered int keys

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