CWICR Historical Cost Tracker
Business Case
Problem Statement
Improving estimates requires:
- Actual cost feedback
- Historical comparisons
- Trend analysis
- Lessons learned
Solution
Track actual costs against CWICR estimates, build historical database, and use data to improve future estimating accuracy.
Business Value
- Accuracy improvement - Learn from actuals
- Benchmarking - Project comparisons
- Trend analysis - Cost movement patterns
- Organizational knowledge - Cost database
Technical Implementation
import pandas as pd
import numpy as np
from typing import Dict, Any, List, Optional
from dataclasses import dataclass, field
from datetime import datetime, date
from enum import Enum
import json
class ProjectStatus(Enum):
"""Project status."""
ESTIMATED = "estimated"
IN_PROGRESS = "in_progress"
COMPLETED = "completed"
CANCELLED = "cancelled"
@dataclass
class CostRecord:
"""Historical cost record."""
project_id: str
project_name: str
work_item_code: str
quantity: float
estimated_cost: float
actual_cost: float
variance: float
variance_percent: float
completion_date: date
notes: str = ""
@dataclass
class ProjectCostSummary:
"""Project cost summary."""
project_id: str
project_name: str
project_type: str
location: str
status: ProjectStatus
estimated_total: float
actual_total: float
variance: float
variance_percent: float
start_date: date
completion_date: Optional[date]
item_count: int
class CWICRHistoricalCost:
"""Track historical costs using CWICR data."""
def __init__(self, cwicr_data: pd.DataFrame = None):
self.cwicr = cwicr_data
self._projects: Dict[str, ProjectCostSummary] = {}
self._records: List[CostRecord] = []
if cwicr_data is not None:
self._index_cwicr()
def _index_cwicr(self):
"""Index CWICR data."""
if 'work_item_code' in self.cwicr.columns:
self._cwicr_index = self.cwicr.set_index('work_item_code')
else:
self._cwicr_index = None
def add_project(self,
project_id: str,
project_name: str,
project_type: str,
location: str,
estimated_total: float,
start_date: date) -> str:
"""Add new project to historical database."""
summary = ProjectCostSummary(
project_id=project_id,
project_name=project_name,
project_type=project_type,
location=location,
status=ProjectStatus.ESTIMATED,
estimated_total=estimated_total,
actual_total=0,
variance=0,
variance_percent=0,
start_date=start_date,
completion_date=None,
item_count=0
)
self._projects[project_id] = summary
return project_id
def record_actual_cost(self,
project_id: str,
work_item_code: str,
quantity: float,
actual_cost: float,
completion_date: date = None,
notes: str = "") -> CostRecord:
"""Record actual cost for work item."""
# Get estimated cost from CWICR
estimated_unit_cost = 0
if self._cwicr_index is not None and work_item_code in self._cwicr_index.index:
item = self._cwicr_index.loc[work_item_code]
labor = float(item.get('labor_cost', 0) or 0)
material = float(item.get('material_cost', 0) or 0)
equipment = float(item.get('equipment_cost', 0) or 0)
estimated_unit_cost = labor + material + equipment
estimated_cost = estimated_unit_cost * quantity
variance = actual_cost - estimated_cost
variance_pct = (variance / estimated_cost * 100) if estimated_cost > 0 else 0
record = CostRecord(
project_id=project_id,
project_name=self._projects.get(project_id, {}).project_name if project_id in self._projects else "",
work_item_code=work_item_code,
quantity=quantity,
estimated_cost=round(estimated_cost, 2),
actual_cost=round(actual_cost, 2),
variance=round(variance, 2),
variance_percent=round(variance_pct, 1),
completion_date=completion_date or date.today(),
notes=notes
)
self._records.append(record)
# Update project summary
if project_id in self._projects:
proj = self._projects[project_id]
proj.actual_total += actual_cost
proj.variance = proj.actual_total - proj.estimated_total
proj.variance_percent = (proj.variance / proj.estimated_total * 100) if proj.estimated_total > 0 else 0
proj.item_count += 1
proj.status = ProjectStatus.IN_PROGRESS
return record
def complete_project(self, project_id: str, completion_date: date = None):
"""Mark project as completed."""
if project_id in self._projects:
self._projects[project_id].status = ProjectStatus.COMPLETED
self._projects[project_id].completion_date = completion_date or date.today()
def get_work_item_history(self, work_item_code: str) -> Dict[str, Any]:
"""Get historical data for specific work item."""
records = [r for r in self._records if r.work_item_code == work_item_code]
if not records:
return {'work_item_code': work_item_code, 'records': 0}
variances = [r.variance_percent for r in records]
actual_costs = [r.actual_cost / r.quantity if r.quantity > 0 else 0 for r in records]
return {
'work_item_code': work_item_code,
'records': len(records),
'average_variance_pct': round(np.mean(variances), 1),
'variance_std': round(np.std(variances), 1),
'average_actual_unit_cost': round(np.mean(actual_costs), 2),
'min_actual_unit_cost': round(min(actual_costs), 2),
'max_actual_unit_cost': round(max(actual_costs), 2),
'projects': list(set(r.project_id for r in records)),
'trend': 'increasing' if len(records) > 2 and actual_costs[-1] > actual_costs[0] else 'stable'
}
def get_accuracy_metrics(self) -> Dict[str, Any]:
"""Calculate overall estimating accuracy metrics."""
if not self._records:
return {}
variances = [r.variance_percent for r in self._records]
# Accuracy by category
by_category = {}
for record in self._records:
category = record.work_item_code.split('-')[0] if '-' in record.work_item_code else 'Other'
if category not in by_category:
by_category[category] = []
by_category[category].append(record.variance_percent)
category_accuracy = {
cat: {
'average_variance': round(np.mean(vals), 1),
'count': len(vals)
}
for cat, vals in by_category.items()
}
return {
'total_records': len(self._records),
'average_variance_pct': round(np.mean(variances), 1),
'variance_std': round(np.std(variances), 1),
'within_5pct': sum(1 for v in variances if abs(v) <= 5) / len(variances) * 100,
'within_10pct': sum(1 for v in variances if abs(v) <= 10) / len(variances) * 100,
'overestimated_pct': sum(1 for v in variances if v < 0) / len(variances) * 100,
'underestimated_pct': sum(1 for v in variances if v > 0) / len(variances) * 100,
'by_category': category_accuracy
}
def suggest_adjustment_factors(self) -> Dict[str, float]:
"""Suggest adjustment factors based on historical variance."""
factors = {}
for record in self._records:
category = record.work_item_code.split('-')[0] if '-' in record.work_item_code else 'Other'
if category not in factors:
factors[category] = []
if record.estimated_cost > 0:
actual_factor = record.actual_cost / record.estimated_cost
factors[category].append(actual_factor)
return {
cat: round(np.mean(vals), 3)
for cat, vals in factors.items()
if len(vals) >= 3 # Require minimum data points
}
def compare_projects(self,
project_ids: List[str] = None) -> pd.DataFrame:
"""Compare multiple projects."""
if project_ids:
projects = [self._projects[pid] for pid in project_ids if pid in self._projects]
else:
projects = list(self._projects.values())
if not projects:
return pd.DataFrame()
return pd.DataFrame([
{
'Project ID': p.project_id,
'Project Name': p.project_name,
'Type': p.project_type,
'Location': p.location,
'Status': p.status.value,
'Estimated': p.estimated_total,
'Actual': p.actual_total,
'Variance': p.variance,
'Variance %': p.variance_percent,
'Items': p.item_count
}
for p in projects
])
def get_benchmarks_by_type(self, project_type: str) -> Dict[str, Any]:
"""Get cost benchmarks for project type."""
projects = [p for p in self._projects.values() if p.project_type == project_type]
if not projects:
return {}
actuals = [p.actual_total for p in projects if p.status == ProjectStatus.COMPLETED]
return {
'project_type': project_type,
'completed_projects': len(actuals),
'average_cost': round(np.mean(actuals), 2) if actuals else 0,
'min_cost': round(min(actuals), 2) if actuals else 0,
'max_cost': round(max(actuals), 2) if actuals else 0,
'average_variance': round(np.mean([p.variance_percent for p in projects]), 1)
}
def export_historical_data(self, output_path: str) -> str:
"""Export historical data to Excel."""
with pd.ExcelWriter(output_path, engine='openpyxl') as writer:
# Projects
if self._projects:
projects_df = self.compare_projects()
projects_df.to_excel(writer, sheet_name='Projects', index=False)
# Records
if self._records:
records_df = pd.DataFrame([
{
'Project': r.project_id,
'Work Item': r.work_item_code,
'Quantity': r.quantity,
'Estimated': r.estimated_cost,
'Actual': r.actual_cost,
'Variance': r.variance,
'Variance %': r.variance_percent,
'Date': r.completion_date,
'Notes': r.notes
}
for r in self._records
])
records_df.to_excel(writer, sheet_name='Records', index=False)
# Accuracy metrics
metrics = self.get_accuracy_metrics()
if metrics:
metrics_df = pd.DataFrame([{
'Total Records': metrics.get('total_records', 0),
'Avg Variance %': metrics.get('average_variance_pct', 0),
'Within 5%': f"{metrics.get('within_5pct', 0):.1f}%",
'Within 10%': f"{metrics.get('within_10pct', 0):.1f}%"
}])
metrics_df.to_excel(writer, sheet_name='Accuracy', index=False)
return output_path
def save_database(self, filepath: str):
"""Save historical database to JSON."""
data = {
'projects': {
pid: {
'project_id': p.project_id,
'project_name': p.project_name,
'project_type': p.project_type,
'location': p.location,
'status': p.status.value,
'estimated_total': p.estimated_total,
'actual_total': p.actual_total,
'start_date': p.start_date.isoformat(),
'completion_date': p.completion_date.isoformat() if p.completion_date else None
}
for pid, p in self._projects.items()
},
'records': [
{
'project_id': r.project_id,
'work_item_code': r.work_item_code,
'quantity': r.quantity,
'estimated_cost': r.estimated_cost,
'actual_cost': r.actual_cost,
'completion_date': r.completion_date.isoformat(),
'notes': r.notes
}
for r in self._records
]
}
with open(filepath, 'w') as f:
json.dump(data, f, indent=2)Quick Start
from datetime import date
# Load CWICR data
cwicr = pd.read_parquet("ddc_cwicr_en.parquet")
# Initialize tracker
tracker = CWICRHistoricalCost(cwicr)
# Add project
tracker.add_project(
project_id="PROJ-001",
project_name="Office Building A",
project_type="commercial",
location="New York",
estimated_total=5000000,
start_date=date(2024, 1, 1)
)
# Record actual costs
tracker.record_actual_cost(
project_id="PROJ-001",
work_item_code="CONC-001",
quantity=200,
actual_cost=32000,
notes="Slightly over due to overtime"
)Common Use Cases
1. Accuracy Analysis
metrics = tracker.get_accuracy_metrics()
print(f"Within 10%: {metrics['within_10pct']:.1f}%")2. Adjustment Factors
factors = tracker.suggest_adjustment_factors()
for cat, factor in factors.items():
print(f"{cat}: {factor:.2f}x")3. Work Item History
history = tracker.get_work_item_history("CONC-001")
print(f"Average variance: {history['average_variance_pct']}%")Resources
- GitHub: OpenConstructionEstimate-DDC-CWICR
- DDC Book: Chapter 3.2 - Historical Cost Analysis