Data Cleaning
Most analysis value is in the cleaning.
Install 安装
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---
name: Data Cleaning
description: Most analysis value is in the cleaning.
---
# Data Cleaning
Real-world data is messy: missing values, inconsistent formats, duplicates, units that differ across sources. Skipping cleaning produces confident wrong answers. It is unglamorous but where most of the truth lives.
## Steps
- **Profile first.** Look at distributions, value counts, and types before touching anything. Surprises here (negative ages, future dates) reveal data-entry bugs.
- **Handle missingness explicitly.** Drop, impute, or model — but decide deliberately. "Default to zero" silently corrupts analysis.
- **Standardize units and formats.** Dates in ISO 8601; currency normalized; casing consistent. Inconsistent formats are invisible until they break a join.
- **Deduplicate.** Real duplicates (same record) vs near-duplicates (same entity, slightly different) need different handling.
- **Document every transformation.** A pipeline you can't reproduce is one you can't trust or debug.