pronto

Summary

This is a project for a code challenge:

Write a program in whatever language you prefer that takes an array of integers and decides whether those integers conform to Benford's Law.

This project was written in PHP 7.4. It exists within a bare-bones RESTful API mini-framework that I previously wrote for testing sample code through Postman HTTP requests.

The margin of error is calculated for each distribution of a leading digit (1-9). If the actual distribution percentage is within the expected distribution percentage plus or minus the margin of error, the assumption is made that the distribution of that leading digit conforms to Benford's law.

Project Structure

Environment variables go into /config/.env and newly-required .env definitions are checked into /config/bootstrap.php
Routes for all endpoints are declared in /public/index.php
PSR4 namespacing is used in the src directory for all other project-related files
- e.g., The Davidwyly\Pronto\Http\Controller\TestController class is located at /src/Davidwyly/Pronto/Http/Controller/TestController.php
Tests are located in /tests
- Test fixtures in /tests/fixtures
- Mock objects are located in /src/Davidwyly/Pronto/Mock

Installation

While this project does not have to be installed in order to be evaluated, I have set up docker so that you can more easily run and test the service yourself.

These installation instructions assume that the following is already installed on your dev environment:

Git
Composer
Docker
Docker Compose
Postman

Git

Navigate to your home directory
- cd ~
Clone down the project
- git clone git@github.com:davidwyly/pronto

Bash Aliases

Ensure you're in the root directory
- cd ~/pronto
Run source .bash_aliases
To view all alias commands for this project, run cat .bash_aliases

Composer

Ensure you're in the root directory
- cd ~/pronto
Composer install
- composer install

Docker

Open up a new terminal
Navigate to the root directory
- cd ~/pronto
Build your containers
- docker-compose up --build

Tests

Ensure you're in the root directory
- cd ~/pronto
Run the PHPUnit tests
- run_tests

Postman

Import collection from ~/pronto/storage/Pronto.postman_collection.json
Set up a new postman environment
1. Click the gear icon in top-right corner
2. Click Add
3. Create an environment name
4. Add a url variable with localhost:8080 as the initial value
5. Click Add
6. Select the environment from the drop-down in the top-right corner
Requests can be found within the Pronto collection

Fibonacci Endpoint Results

{
    "sample-size": 1000,
    "z-score": 0.4621525165147706,
    "standard-deviation": 2.460911840575985,
    "1": {
        "expected": "30.103%",
        "actual": "30.1%",
        "variance": "-0.003%",
        "margin-of-error": "0.6704%",
        "conforms-to-benford's-law": true
    },
    "2": {
        "expected": "17.6091%",
        "actual": "17.7%",
        "variance": "0.0909%",
        "margin-of-error": "0.5578%",
        "conforms-to-benford's-law": true
    },
    "3": {
        "expected": "12.4939%",
        "actual": "12.5%",
        "variance": "0.0061%",
        "margin-of-error": "0.4833%",
        "conforms-to-benford's-law": true
    },
    "4": {
        "expected": "9.691%",
        "actual": "9.6%",
        "variance": "-0.091%",
        "margin-of-error": "0.4305%",
        "conforms-to-benford's-law": true
    },
    "5": {
        "expected": "7.9181%",
        "actual": "8%",
        "variance": "0.0819%",
        "margin-of-error": "0.3965%",
        "conforms-to-benford's-law": true
    },
    "6": {
        "expected": "6.6947%",
        "actual": "6.7%",
        "variance": "0.0053%",
        "margin-of-error": "0.3654%",
        "conforms-to-benford's-law": true
    },
    "7": {
        "expected": "5.7992%",
        "actual": "5.6%",
        "variance": "-0.1992%",
        "margin-of-error": "0.336%",
        "conforms-to-benford's-law": true
    },
    "8": {
        "expected": "5.1153%",
        "actual": "5.3%",
        "variance": "0.1847%",
        "margin-of-error": "0.3274%",
        "conforms-to-benford's-law": true
    },
    "9": {
        "expected": "4.5757%",
        "actual": "4.5%",
        "variance": "-0.0757%",
        "margin-of-error": "0.303%",
        "conforms-to-benford's-law": true
    }
}

Custom Array Endpoint Results

{
    "sample-size": 505,
    "z-score": 1.6379464099227126,
    "standard-deviation": 2.1521345609224443,
    "1": {
        "expected": "30.103%",
        "actual": "14.2574%",
        "variance": "-15.8456%",
        "margin-of-error": "2.5484%",
        "conforms-to-benford's-law": false
    },
    "2": {
        "expected": "17.6091%",
        "actual": "23.7624%",
        "variance": "6.1533%",
        "margin-of-error": "3.1023%",
        "conforms-to-benford's-law": false
    },
    "3": {
        "expected": "12.4939%",
        "actual": "19.2079%",
        "variance": "6.714%",
        "margin-of-error": "2.8713%",
        "conforms-to-benford's-law": false
    },
    "4": {
        "expected": "9.691%",
        "actual": "0%",
        "variance": "-9.691%",
        "margin-of-error": "0%",
        "conforms-to-benford's-law": false
    },
    "5": {
        "expected": "7.9181%",
        "actual": "14.2574%",
        "variance": "6.3393%",
        "margin-of-error": "2.5484%",
        "conforms-to-benford's-law": false
    },
    "6": {
        "expected": "6.6947%",
        "actual": "9.505%",
        "variance": "2.8103%",
        "margin-of-error": "2.1377%",
        "conforms-to-benford's-law": false
    },
    "7": {
        "expected": "5.7992%",
        "actual": "19.0099%",
        "variance": "13.2107%",
        "margin-of-error": "2.86%",
        "conforms-to-benford's-law": false
    },
    "8": {
        "expected": "5.1153%",
        "actual": "0%",
        "variance": "-5.1153%",
        "margin-of-error": "0%",
        "conforms-to-benford's-law": false
    },
    "9": {
        "expected": "4.5757%",
        "actual": "0%",
        "variance": "-4.5757%",
        "margin-of-error": "0%",
        "conforms-to-benford's-law": false
    }
}

davidwyly/pronto