# `monthly_to_quarterly_rule`

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> Axis ``monthly_to_quarterly_rule`` on sub-layer ``l2_a`` (layer ``l2``).

## Sub-layer

**l2_a**

## Axis metadata

- Default: `'quarterly_average'`
- Sweepable: True
- Status: operational

## Operational status summary

- Operational: 3 option(s)
- Future: 0 option(s)

## Options

### `quarterly_average`  --  operational

Aggregate to quarterly via mean of the three monthly observations.

See [quarterly_average function page](../monthly_to_quarterly_rule/quarterly_average.md) for full documentation + parameters + standalone usage. Standalone: ``mf.functions.freq_align_monthly_to_quarterly_clean``.

### `quarterly_endpoint`  --  operational

Aggregate via the end-of-quarter observation.

Use for series that snap to a quarter-end (e.g., balance-sheet data).

Configures the ``monthly_to_quarterly_rule`` axis on ``l2_a`` (layer ``l2``); the ``quarterly_endpoint`` value is materialised in the recipe's ``fixed_axes`` block under that sub-layer.

**When to use**

End-of-period stocks (M2 month-end, balance-sheet series).

**References**

* macroforecast design Part 2, L2: 'preprocessing is the only layer with a strict A→B→C→D→E execution order; every cell follows the same pipeline.'

**Related options**: [`quarterly_average`](#quarterly-average), [`quarterly_sum`](#quarterly-sum)

_Last reviewed 2026-05-04 by macroforecast author._

### `quarterly_sum`  --  operational

Aggregate via the sum of the three monthly observations.

Standard for flow variables (production, sales, payroll growth).

Configures the ``monthly_to_quarterly_rule`` axis on ``l2_a`` (layer ``l2``); the ``quarterly_sum`` value is materialised in the recipe's ``fixed_axes`` block under that sub-layer.

**When to use**

Flow variables; cumulative-quantity series.

**References**

* macroforecast design Part 2, L2: 'preprocessing is the only layer with a strict A→B→C→D→E execution order; every cell follows the same pipeline.'

**Related options**: [`quarterly_average`](#quarterly-average), [`quarterly_endpoint`](#quarterly-endpoint)

_Last reviewed 2026-05-04 by macroforecast author._