data-analysis

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---
name: data-analysis
description: Use this skill when the user uploads Excel (.xlsx/.xls) or CSV files and wants to perform data analysis, generate statistics, create summaries, pivot tables, SQL queries, or any form of structured data exploration. Supports multi-sheet Excel workbooks, aggregation, filtering, joins, and exporting results to CSV/JSON/Markdown.
---

# Data Analysis Skill

## Overview

This skill analyzes user-uploaded Excel/CSV files using DuckDB — an in-process analytical SQL engine. It supports schema inspection, SQL-based querying, statistical summaries, and result export, all through a single Python script.

## Core Capabilities

- Inspect Excel/CSV file structure (sheets, columns, types, row counts)
- Execute arbitrary SQL queries against uploaded data
- Generate statistical summaries (mean, median, stddev, percentiles, nulls)
- Support multi-sheet Excel workbooks (each sheet becomes a table)
- Export query results to CSV, JSON, or Markdown
- Handle large files efficiently with DuckDB's columnar engine

## Workflow

### Step 1: Understand Requirements

When a user uploads data files and requests analysis, identify:

- **File location**: Path(s) to uploaded Excel/CSV files under `/mnt/user-data/uploads/`
- **Analysis goal**: What insights the user wants (summary, filtering, aggregation, comparison, etc.)
- **Output format**: How results should be presented (table, CSV export, JSON, etc.)
- You don't need to check the folder under `/mnt/user-data`

### Step 2: Inspect File Structure

First, inspect the uploaded file to understand its schema:

```bash
python /mnt/skills/public/data-analysis/scripts/analyze.py \
  --files /mnt/user-data/uploads/data.xlsx \
  --action inspect
```

This returns:
- Sheet names (for Excel) or filename (for CSV)
- Column names, data types, and non-null counts
- Row count per sheet/file
- Sample data (first 5 rows)

### Step 3: Perform Analysis

Based on the schema, construct SQL queries to answer the user's questions.

#### Run SQL Query

```bash
python /mnt/skills/public/data-analysis/scripts/analyze.py \
  --files /mnt/user-data/uploads/data.xlsx \
  --action query \
  --sql "SELECT category, COUNT(*) as count, AVG(amount) as avg_amount FROM Sheet1 GROUP BY category ORDER BY count DESC"
```

#### Generate Statistical Summary

```bash
python /mnt/skills/public/data-analysis/scripts/analyze.py \
  --files /mnt/user-data/uploads/data.xlsx \
  --action summary \
  --table Sheet1
```

This returns for each numeric column: count, mean, std, min, 25%, 50%, 75%, max, null_count.
For string columns: count, unique, top value, frequency, null_count.

#### Export Results

```bash
python /mnt/skills/public/data-analysis/scripts/analyze.py \
  --files /mnt/user-data/uploads/data.xlsx \
  --action query \
  --sql "SELECT * FROM Sheet1 WHERE amount > 1000" \
  --output-file /mnt/user-data/outputs/filtered-results.csv
```

Supported output formats (auto-detected from extension):
- `.csv` — Comma-separated values
- `.json` — JSON array of records
- `.md` — Markdown table

### Parameters

| Parameter | Required | Description |
|-----------|----------|-------------|
| `--files` | Yes | Space-separated paths to Excel/CSV files |
| `--action` | Yes | One of: `inspect`, `query`, `summary` |
| `--sql` | For `query` | SQL query to execute |
| `--table` | For `summary` | Table/sheet name to summarize |
| `--output-file` | No | Path to export results (CSV/JSON/MD) |

> [!NOTE]
> Do NOT read the Python file, just call it with the parameters.

## Table Naming Rules

- **Excel files**: Each sheet becomes a table named after the sheet (e.g., `Sheet1`, `Sales`, `Revenue`)
- **CSV files**: Table name is the filename without extension (e.g., `data.csv` → `data`)
- **Multiple files**: All tables from all files are available in the same query context, enabling cross-file joins
- **Special characters**: Sheet/file names with spaces or special characters are auto-sanitized (spaces → underscores). Use double quotes