# Dax

> Create, review, and document Power BI DAX measures for KPIs, ratios, time intelligence, and business analytics. Use when writing or validating DAX.

- Skill: `onlinesourdough/dax` (Agent Skill)
- Install (CLI): `npx skillmds@latest add onlinesourdough/dax`
- Raw SKILL.md: https://api.skillmd.com/api/skills/onlinesourdough/dax/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Data & Analytics
- Author: onlinesourdough (https://skillmd.com/u/onlinesourdough)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/onlinesourdough/dax

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# DAX Measures

## Workflow

1. Define the measure in business language.
2. Identify required tables/columns and filter context.
3. Prefer base measures + derived measures.
4. Add format string, description, and display folder.
5. Validate with a DAX query/tool when possible.

For a changed KPI, use the
[canonical regression recipe](../../../docs/validation.md#representative-data-domain-regressions).
Its KPI case must cover the relevant filter context and any changed base/derived
measure boundary. If native DAX execution is unavailable or out of scope,
record that gap and use the closest safe inspection or deterministic proof;
do not claim a query ran.

## Patterns

- Use `DIVIDE()` for ratios.
- Use variables for readability.
- Avoid unnecessary row-by-row iterators.
- Explain `CALCULATE()` filter changes.
- Confirm date table before time intelligence.

## Output format

```text
Name:
Business definition:
DAX:
Format string:
Display folder:
Description:
Validation idea:
```

Do not edit model files unless the target table/file is clear.