using-formula-modifiers
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
With your agent
Install OMGSkills skill "gopigment/ai-plugins:skills/using-formula-modifiers" into this agent's normal skills directory: call the OMGSkills MCP get_install_plan tool for your agent and run the script it returns (it installs only the pinned commit and verifies SKILL.md), and stop if MCP or the pin is unavailable. Do not overwrite or change existing skills without asking me.
Manual command
git clone https://github.com/gopigment/ai-plugins /tmp/ai-plugins && ln -s /tmp/ai-plugins/skills/using-formula-modifiers ~/.claude/skills/using-formula-modifiersFrom 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.