# using-formula-modifiers

> Claude/Codex skill by [@gopigment](https://omgskills.com/library/gopigment/index.md) · 23 stars · Updated 2026-10-23

Execution skill. Use when a formula's source metric dimensions differ from the target metric — apply BY, ADD, REMOVE, KEEP, SELECT, FILTER, EXCLUDE, TOPARENTLIST, or TOSUBSET. Also covers arrow-mapping syntax (BY ... -\>) and tiered lookup patterns.

## Install

```sh
git clone https://github.com/gopigment/ai-plugins /tmp/ai-plugins && ln -s /tmp/ai-plugins/skills/using-formula-modifiers ~/.claude/skills/using-formula-modifiers
```

## From README

Apply Formula Modifiers Modifiers appear in square brackets after an expression: expression\[MODIFIER: argument\]. They change dimensionality or filter data so a source metric aligns with the target metric. Distinguish Source from Target Source — the metric or expression you reference (right of =). Target — the metric whose formula you are writing; its dimension list defines the output shape. Every modifier maps source dimensions toward target dimensions. Check target dimensions first, then pick modifiers. Dimension Relationship Types | Source→Target | Type | Modifier | Methods | | --- | --- | --- | --- | | N→1 | Aggregation | BY | SUM, AVG, MIN, MAX, COUNT | | N→none | Aggregation | REMOVE | SUM, AVG, MIN, MAX, COUNT | | N→none (filtered) | Conditional agg. | SELECT | SUM, AVG, MIN, MAX, COUNT | | 1→N | Allocation | BY | CONSTANT, SPLIT | | none→N | Allocation | ADD | CONSTANT, SPLIT | | Defaults: SUM for aggregation, CONSTANT for allocation.

## Links

- HTML page: https://omgskills.com/library/gopigment/ai-plugins/skills/using-formula-modifiers/
- GitHub: https://github.com/gopigment/ai-plugins
- Author: [@gopigment](https://omgskills.com/library/gopigment/index.md)

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