# Use Counter Frequency

> For counting and frequency: histograms, most common elements, vote tallying, neighbor counting, word frequencies, distribution analysis.

- **Type:** Skill
- **Install:** `agentstack add skill-jimmc414-claude-code-plugin-marketplace-use-counter-frequency`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [jimmc414](https://agentstack.voostack.com/s/jimmc414)
- **Installs:** 0
- **Category:** [AI & ML](https://agentstack.voostack.com/c/ai-and-ml)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [jimmc414](https://github.com/jimmc414)
- **Source:** https://github.com/jimmc414/claude-code-plugin-marketplace/tree/master/plugins/norvig-patterns/skills/use-counter-frequency

## Install

```sh
agentstack add skill-jimmc414-claude-code-plugin-marketplace-use-counter-frequency
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# use-counter-frequency

## When to Use
- Counting occurrences of items
- Finding most common elements
- Building histograms
- Vote/tally counting
- Word frequency analysis
- Neighbor counting in grids
- Any "how many of each" question

## When NOT to Use
- When you need the items themselves, not counts
- Single occurrence checking (use set)
- When counts need to be updated in complex ways

## The Pattern

Use `collections.Counter` - a dict subclass optimized for counting.

```python
from collections import Counter

# Count anything iterable
Counter('abracadabra')  # {'a': 5, 'b': 2, 'r': 2, 'c': 1, 'd': 1}
Counter([1, 1, 2, 3, 3, 3])  # {3: 3, 1: 2, 2: 1}

# Most common
counter.most_common(3)  # Top 3 as [(item, count), ...]

# Arithmetic
Counter('abc') + Counter('bcd')  # {'b': 2, 'c': 2, 'a': 1, 'd': 1}

# Total count
sum(counter.values())
```

## Example (from pytudes)

```python
from collections import Counter

# Word frequency from text (spell.py)
def words(text):
    return re.findall(r'\w+', text.lower())

WORDS = Counter(words(open('big.txt').read()))
# WORDS['the'] = 79809

def P(word, N=sum(WORDS.values())):
    """Probability of word."""
    return WORDS[word] / N

# Neighbor counting (Life.ipynb)
def neighbor_counts(world):
    """For each cell, count how many live neighbors it has."""
    return Counter(neighbor
                   for cell in world
                   for neighbor in neighbors(cell))

# Use for Game of Life rules
counts = neighbor_counts(world)
new_world = {cell for cell, count in counts.items()
             if count == 3 or (count == 2 and cell in world)}

# Probability distribution (Probability.ipynb)
class Dist(Counter):
    """A distribution of {outcome: frequency}."""
    pass

DK = Dist(GG=121801, GB=126840, BG=127123, BB=135138)
# Access: DK['GG'], DK.most_common(), sum(DK.values())
```

## Key Principles
1. **Counter is a dict**: All dict methods work
2. **Missing keys = 0**: No KeyError for missing items
3. **most_common(n)**: Get top n items efficiently
4. **Arithmetic works**: Add, subtract, intersect counters
5. **Generator input**: `Counter(x for x in iterable if condition)`

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [jimmc414](https://github.com/jimmc414)
- **Source:** [jimmc414/claude-code-plugin-marketplace](https://github.com/jimmc414/claude-code-plugin-marketplace)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-jimmc414-claude-code-plugin-marketplace-use-counter-frequency
- Seller: https://agentstack.voostack.com/s/jimmc414
- Browse the marketplace: https://agentstack.voostack.com/browse

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Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.