data-anomaly-detector

What this skill does

# Data Anomaly Detector for Construction

## Overview

Detect unusual patterns, outliers, and anomalies in construction data. Identify cost overruns, schedule delays, productivity issues, and data quality problems before they impact projects.

## Business Case

Construction data often contains anomalies that indicate:
- Cost estimate errors or fraud
- Schedule logic issues
- Productivity problems
- Data entry mistakes
- Equipment or material issues

Early detection prevents costly corrections and project delays.

## Technical Implementation

```python
from dataclasses import dataclass, field
from typing import List, Dict, Any, Optional, Tuple
from enum import Enum
import pandas as pd
import numpy as np
from datetime import datetime
from scipy import stats

class AnomalyType(Enum):
    OUTLIER = "outlier"
    PATTERN_BREAK = "pattern_break"
    MISSING_SEQUENCE = "missing_sequence"
    DUPLICATE = "duplicate"
    IMPOSSIBLE_VALUE = "impossible_value"
    TREND_DEVIATION = "trend_deviation"

class AnomalySeverity(Enum):
    CRITICAL = "critical"
    HIGH = "high"
    MEDIUM = "medium"
    LOW = "low"

@dataclass
class Anomaly:
    id: str
    anomaly_type: AnomalyType
    severity: AnomalySeverity
    field: str
    value: Any
    expected_range: Optional[Tuple[float, float]] = None
    description: str = ""
    row_index: Optional[int] = None
    detection_method: str = ""
    confidence: float = 0.0
    suggested_action: str = ""

@dataclass
class AnomalyReport:
    source: str
    detected_at: datetime
    total_records: int
    anomalies: List[Anomaly]
    summary: Dict[str, int]

class ConstructionAnomalyDetector:
    """Detect anomalies in construction data."""

    # Construction-specific thresholds
    COST_THRESHOLDS = {
        'concrete_per_cy': (200, 800),
        'steel_per_ton': (1500, 4000),
        'labor_per_hour': (25, 150),
        'overhead_percentage': (5, 25),
        'contingency_percentage': (3, 20),
    }

    SCHEDULE_THRESHOLDS = {
        'max_activity_duration': 365,  # days
        'max_lag': 30,  # days
        'min_productivity': 0.1,
        'max_productivity': 10.0,
    }

    def __init__(self):
        self.anomalies: List[Anomaly] = []
        self.detection_history: List[AnomalyReport] = []

    def detect_cost_anomalies(self, df: pd.DataFrame, cost_column: str,
                              group_by: str = None) -> List[Anomaly]:
        """Detect anomalies in cost data."""
        anomalies = []

        # Statistical outlier detection (IQR method)
        Q1 = df[cost_column].quantile(0.25)
        Q3 = df[cost_column].quantile(0.75)
        IQR = Q3 - Q1
        lower_bound = Q1 - 1.5 * IQR
        upper_bound = Q3 + 1.5 * IQR

        outliers = df[(df[cost_column] < lower_bound) | (df[cost_column] > upper_bound)]

        for idx, row in outliers.iterrows():
            value = row[cost_column]
            severity = AnomalySeverity.HIGH if abs(value - df[cost_column].median()) > 3 * IQR else AnomalySeverity.MEDIUM

            anomalies.append(Anomaly(
                id=f"COST-{idx}",
                anomaly_type=AnomalyType.OUTLIER,
                severity=severity,
                field=cost_column,
                value=value,
                expected_range=(lower_bound, upper_bound),
                description=f"Cost value {value:,.2f} outside expected range",
                row_index=idx,
                detection_method="IQR",
                confidence=0.95,
                suggested_action="Review cost estimate for errors"
            ))

        # Negative cost check
        negatives = df[df[cost_column] < 0]
        for idx, row in negatives.iterrows():
            anomalies.append(Anomaly(
                id=f"COST-NEG-{idx}",
                anomaly_type=AnomalyType.IMPOSSIBLE_VALUE,
                severity=AnomalySeverity.CRITICAL,
                field=cost_column,
                value=row[cost_column],
                expected_range=(0, None),
                description="Negative cost value detected",
                row_index=idx,
                detection_method="Business Rule",
                confidence=1.0,
                suggested_action="Correct data entry error or investigate credit"
            ))

        # Group-based anomalies (if grouped)
        if group_by and group_by in df.columns:
            group_stats = df.groupby(group_by)[cost_column].agg(['mean', 'std'])

            for group_name, stats in group_stats.iterrows():
                group_data = df[df[group_by] == group_name]
                z_scores = np.abs((group_data[cost_column] - stats['mean']) / stats['std'])

                for idx, z in z_scores.items():
                    if z > 3:
                        anomalies.append(Anomaly(
                            id=f"COST-GROUP-{idx}",
                            anomaly_type=AnomalyType.OUTLIER,
                            severity=AnomalySeverity.MEDIUM,
                            field=cost_column,
                            value=df.loc[idx, cost_column],
                            description=f"Unusual cost for group {group_name} (z-score: {z:.2f})",
                            row_index=idx,
                            detection_method="Z-Score by Group",
                            confidence=min(z / 5, 1.0)
                        ))

        return anomalies

    def detect_schedule_anomalies(self, df: pd.DataFrame) -> List[Anomaly]:
        """Detect anomalies in schedule data."""
        anomalies = []

        # Check for required columns
        required = ['start_date', 'end_date']
        if not all(col in df.columns for col in required):
            return anomalies

        # Convert dates
        df['start_date'] = pd.to_datetime(df['start_date'])
        df['end_date'] = pd.to_datetime(df['end_date'])

        # Calculate duration
        df['duration'] = (df['end_date'] - df['start_date']).dt.days

        # Negative duration (end before start)
        negative_duration = df[df['duration'] < 0]
        for idx, row in negative_duration.iterrows():
            anomalies.append(Anomaly(
                id=f"SCHED-NEG-{idx}",
                anomaly_type=AnomalyType.IMPOSSIBLE_VALUE,
                severity=AnomalySeverity.CRITICAL,
                field="duration",
                value=row['duration'],
                description="End date before start date",
                row_index=idx,
                detection_method="Business Rule",
                confidence=1.0,
                suggested_action="Correct dates"
            ))

        # Extremely long durations
        long_tasks = df[df['duration'] > self.SCHEDULE_THRESHOLDS['max_activity_duration']]
        for idx, row in long_tasks.iterrows():
            anomalies.append(Anomaly(
                id=f"SCHED-LONG-{idx}",
                anomaly_type=AnomalyType.OUTLIER,
                severity=AnomalySeverity.MEDIUM,
                field="duration",
                value=row['duration'],
                expected_range=(0, self.SCHEDULE_THRESHOLDS['max_activity_duration']),
                description=f"Task duration {row['duration']} days exceeds threshold",
                row_index=idx,
                detection_method="Threshold",
                confidence=0.9,
                suggested_action="Review if task should be broken down"
            ))

        # Zero duration non-milestones
        if 'is_milestone' in df.columns:
            zero_duration = df[(df['duration'] == 0) & (~df['is_milestone'])]
            for idx, row in zero_duration.iterrows():
                anomalies.append(Anomaly(
                    id=f"SCHED-ZERO-{idx}",
                    anomaly_type=AnomalyType.IMPOSSIBLE_VALUE,
                    severity=AnomalySeverity.HIGH,