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 for names that start with numbers or contain special characters, e.g.,
```
"2024_Sales"
```

Analysis Patterns

Basic Exploration

sql

-- Row count
SELECT COUNT(*) FROM Sheet1

-- Distinct values in a column
SELECT DISTINCT category FROM Sheet1

-- Value distribution
SELECT category, COUNT(*) as cnt FROM Sheet1 GROUP BY category ORDER BY cnt DESC

-- Date range
SELECT MIN(date_col), MAX(date_col) FROM Sheet1

Aggregation & Grouping

sql

-- Revenue by category and month
SELECT category, DATE_TRUNC('month', order_date) as month,
       SUM(revenue) as total_revenue
FROM Sales
GROUP BY category, month
ORDER BY month, total_revenue DESC

-- Top 10 customers by spend
SELECT customer_name, SUM(amount) as total_spend
FROM Orders GROUP BY customer_name
ORDER BY total_spend DESC LIMIT 10

Cross-file Joins

sql

-- Join sales with customer info from different files
SELECT s.order_id, s.amount, c.customer_name, c.region
FROM sales s
JOIN customers c ON s.customer_id = c.id
WHERE s.amount > 500

Window Functions

sql

-- Running total and rank
SELECT order_date, amount,
       SUM(amount) OVER (ORDER BY order_date) as running_total,
       RANK() OVER (ORDER BY amount DESC) as amount_rank
FROM Sales

Pivot-style Analysis

sql

-- Pivot: monthly revenue by category
SELECT category,
       SUM(CASE WHEN MONTH(date) = 1 THEN revenue END) as Jan,
       SUM(CASE WHEN MONTH(date) = 2 THEN revenue END) as Feb,
       SUM(CASE WHEN MONTH(date) = 3 THEN revenue END) as Mar
FROM Sales
GROUP BY category

Complete Example

User uploads

sales_2024.xlsx

(with sheets:

Orders

Products

Customers

) and asks: "Analyze my sales data — show top products by revenue and monthly trends."

Step 1: Inspect the file

bash

python /mnt/skills/public/data-analysis/scripts/analyze.py \
  --files /mnt/user-data/uploads/sales_2024.xlsx \
  --action inspect

Step 2: Top products by revenue

bash

python /mnt/skills/public/data-analysis/scripts/analyze.py \
  --files /mnt/user-data/uploads/sales_2024.xlsx \
  --action query \
  --sql "SELECT p.product_name, SUM(o.quantity * o.unit_price) as total_revenue, SUM(o.quantity) as total_units FROM Orders o JOIN Products p ON o.product_id = p.id GROUP BY p.product_name ORDER BY total_revenue DESC LIMIT 10"

Step 3: Monthly revenue trends

bash

python /mnt/skills/public/data-analysis/scripts/analyze.py \
  --files /mnt/user-data/uploads/sales_2024.xlsx \
  --action query \
  --sql "SELECT DATE_TRUNC('month', order_date) as month, SUM(quantity * unit_price) as revenue FROM Orders GROUP BY month ORDER BY month" \
  --output-file /mnt/user-data/outputs/monthly-trends.csv

Step 4: Statistical summary

bash

python /mnt/skills/public/data-analysis/scripts/analyze.py \
  --files /mnt/user-data/uploads/sales_2024.xlsx \
  --action summary \
  --table Orders

Present results to the user with clear explanations of findings, trends, and actionable insights.

Multi-file Example

User uploads

orders.csv

and

customers.xlsx

and asks: "Which region has the highest average order value?"

bash

python /mnt/skills/public/data-analysis/scripts/analyze.py \
  --files /mnt/user-data/uploads/orders.csv /mnt/user-data/uploads/customers.xlsx \
  --action query \
  --sql "SELECT c.region, AVG(o.amount) as avg_order_value, COUNT(*) as order_count FROM orders o JOIN Customers c ON o.customer_id = c.id GROUP BY c.region ORDER BY avg_order_value DESC"

Output Handling

After analysis:

Present query results directly in conversation as formatted tables
For large results, export to file and share via
```
present_files
```
tool
Always explain findings in plain language with key takeaways
Suggest follow-up analyses when patterns are interesting
Offer to export results if the user wants to keep them

Caching

The script automatically caches loaded data to avoid re-parsing files on every call:

On first load, files are parsed and stored in a persistent DuckDB database under
```
/mnt/user-data/workspace/.data-analysis-cache/
```
The cache key is a SHA256 hash of all input file contents — if files change, a new cache is created
Subsequent calls with the same files will use the cached database directly (near-instant startup)
Cache is transparent — no extra parameters needed

This is especially useful when running multiple queries against the same data files (inspect → query → summary).

Notes

DuckDB supports full SQL including window functions, CTEs, subqueries, and advanced aggregations
Excel date columns are automatically parsed; use DuckDB date functions (
```
DATE_TRUNC
```
,
```
EXTRACT
```
, etc.)
For very large files (100MB+), DuckDB handles them efficiently without loading everything into memory
Column names with spaces are accessible using double quotes:
```
"Column Name"
```

data-analysis

NPX Install

Tags

SKILL.md Content

Data Analysis Skill

Overview

Core Capabilities

Workflow

Step 1: Understand Requirements

Step 2: Inspect File Structure

Step 3: Perform Analysis

Run SQL Query

Generate Statistical Summary

Export Results

Parameters

Table Naming Rules

Analysis Patterns

Basic Exploration

Aggregation & Grouping

Cross-file Joins

Window Functions

Pivot-style Analysis

Complete Example

Step 1: Inspect the file

Step 2: Top products by revenue

Step 3: Monthly revenue trends

Step 4: Statistical summary

Multi-file Example

Output Handling

Caching

Notes