CWICR Comparison Tool
Business Case
Problem Statement
Project stakeholders need to compare:
- Alternative design options
- Estimate versions over time
- Projects against benchmarks
- Actual vs estimated costs
Solution
Structured comparison of CWICR-based estimates with variance analysis, benchmarking, and visual reporting.
Business Value
- Decision support - Compare alternatives objectively
- Version control - Track estimate evolution
- Benchmarking - Compare against standards
- Audit - Document estimate changes
Technical Implementation
import pandas as pd
import numpy as np
from typing import Dict, Any, List, Optional, Tuple
from dataclasses import dataclass, field
from datetime import datetime
from enum import Enum
class ComparisonType(Enum):
"""Types of comparisons."""
VERSION = "version" # Same project, different versions
ALTERNATIVE = "alternative" # Same project, design alternatives
BENCHMARK = "benchmark" # Project vs standard/benchmark
ACTUAL = "actual" # Estimate vs actual costs
PROJECT = "project" # Different projects
class VarianceSignificance(Enum):
"""Significance level of variance."""
CRITICAL = "critical" # >20% variance
HIGH = "high" # 10-20%
MEDIUM = "medium" # 5-10%
LOW = "low" # <5%
NONE = "none" # No variance
@dataclass
class ComparisonItem:
"""Single item comparison."""
work_item_code: str
description: str
base_quantity: float
base_cost: float
compare_quantity: float
compare_cost: float
quantity_variance: float
quantity_variance_pct: float
cost_variance: float
cost_variance_pct: float
significance: VarianceSignificance
@dataclass
class ComparisonResult:
"""Complete comparison result."""
comparison_type: ComparisonType
base_name: str
compare_name: str
base_total: float
compare_total: float
total_variance: float
total_variance_pct: float
items: List[ComparisonItem]
summary_by_category: Dict[str, Dict[str, float]]
created_at: datetime
class CWICRComparisonTool:
"""Compare CWICR-based estimates."""
SIGNIFICANCE_THRESHOLDS = {
VarianceSignificance.CRITICAL: 0.20,
VarianceSignificance.HIGH: 0.10,
VarianceSignificance.MEDIUM: 0.05,
VarianceSignificance.LOW: 0.01
}
def __init__(self):
pass
def _get_significance(self, variance_pct: float) -> VarianceSignificance:
"""Determine variance significance."""
abs_var = abs(variance_pct) / 100
if abs_var >= self.SIGNIFICANCE_THRESHOLDS[VarianceSignificance.CRITICAL]:
return VarianceSignificance.CRITICAL
elif abs_var >= self.SIGNIFICANCE_THRESHOLDS[VarianceSignificance.HIGH]:
return VarianceSignificance.HIGH
elif abs_var >= self.SIGNIFICANCE_THRESHOLDS[VarianceSignificance.MEDIUM]:
return VarianceSignificance.MEDIUM
elif abs_var >= self.SIGNIFICANCE_THRESHOLDS[VarianceSignificance.LOW]:
return VarianceSignificance.LOW
else:
return VarianceSignificance.NONE
def compare_estimates(self,
base_df: pd.DataFrame,
compare_df: pd.DataFrame,
base_name: str = "Base",
compare_name: str = "Compare",
comparison_type: ComparisonType = ComparisonType.VERSION,
code_column: str = 'work_item_code',
quantity_column: str = 'quantity',
cost_column: str = 'total_cost') -> ComparisonResult:
"""Compare two estimates."""
# Merge on code
merged = base_df.merge(
compare_df,
on=code_column,
how='outer',
suffixes=('_base', '_compare')
)
items = []
for _, row in merged.iterrows():
base_qty = float(row.get(f'{quantity_column}_base', 0) or 0)
base_cost = float(row.get(f'{cost_column}_base', 0) or 0)
compare_qty = float(row.get(f'{quantity_column}_compare', 0) or 0)
compare_cost = float(row.get(f'{cost_column}_compare', 0) or 0)
qty_variance = compare_qty - base_qty
qty_variance_pct = (qty_variance / base_qty * 100) if base_qty > 0 else (100 if compare_qty > 0 else 0)
cost_variance = compare_cost - base_cost
cost_variance_pct = (cost_variance / base_cost * 100) if base_cost > 0 else (100 if compare_cost > 0 else 0)
items.append(ComparisonItem(
work_item_code=str(row.get(code_column, '')),
description=str(row.get('description_base', row.get('description_compare', ''))),
base_quantity=base_qty,
base_cost=base_cost,
compare_quantity=compare_qty,
compare_cost=compare_cost,
quantity_variance=round(qty_variance, 2),
quantity_variance_pct=round(qty_variance_pct, 1),
cost_variance=round(cost_variance, 2),
cost_variance_pct=round(cost_variance_pct, 1),
significance=self._get_significance(cost_variance_pct)
))
# Totals
base_total = sum(i.base_cost for i in items)
compare_total = sum(i.compare_cost for i in items)
total_variance = compare_total - base_total
total_variance_pct = (total_variance / base_total * 100) if base_total > 0 else 0
# Summary by category
summary_by_category = self._summarize_by_category(items, merged)
return ComparisonResult(
comparison_type=comparison_type,
base_name=base_name,
compare_name=compare_name,
base_total=round(base_total, 2),
compare_total=round(compare_total, 2),
total_variance=round(total_variance, 2),
total_variance_pct=round(total_variance_pct, 1),
items=items,
summary_by_category=summary_by_category,
created_at=datetime.now()
)
def _summarize_by_category(self,
items: List[ComparisonItem],
merged_df: pd.DataFrame) -> Dict[str, Dict[str, float]]:
"""Summarize comparison by category."""
summary = {}
# Try to extract category from work item code prefix
for item in items:
code = item.work_item_code
category = code.split('-')[0] if '-' in code else 'Other'
if category not in summary:
summary[category] = {
'base_cost': 0,
'compare_cost': 0,
'variance': 0,
'variance_pct': 0,
'item_count': 0
}
summary[category]['base_cost'] += item.base_cost
summary[category]['compare_cost'] += item.compare_cost
summary[category]['variance'] += item.cost_variance
summary[category]['item_count'] += 1
# Calculate percentages
for category in summary:
base = summary[category]['base_cost']
if base > 0:
summary[category]['variance_pct'] = round(
summary[category]['variance'] / base * 100, 1
)
return summary
def get_significant_variances(self,
result: ComparisonResult,
min_significance: VarianceSignificance = VarianceSignificance.MEDIUM) -> List[ComparisonItem]:
"""Get items with significant variances."""
significance_order = [
VarianceSignificance.CRITICAL,
VarianceSignificance.HIGH,
VarianceSignificance.MEDIUM,
VarianceSignificance.LOW,
VarianceSignificance.NONE
]
min_index = significance_order.index(min_significance)
significant = [
item for item in result.items
if significance_order.index(item.significance) <= min_index
]
return sorted(significant, key=lambda x: abs(x.cost_variance), reverse=True)
def compare_multiple(self,
estimates: List[Tuple[str, pd.DataFrame]],
base_index: int = 0) -> Dict[str, ComparisonResult]:
"""Compare multiple estimates against base."""
base_name, base_df = estimates[base_index]
results = {}
for i, (name, df) in enumerate(estimates):
if i == base_index:
continue
result = self.compare_estimates(
base_df=base_df,
compare_df=df,
base_name=base_name,
compare_name=name,
comparison_type=ComparisonType.ALTERNATIVE
)
results[name] = result
return results
def benchmark_comparison(self,
project_df: pd.DataFrame,
benchmark_df: pd.DataFrame,
project_name: str,
benchmark_name: str = "Industry Benchmark") -> ComparisonResult:
"""Compare project against benchmark."""
return self.compare_estimates(
base_df=benchmark_df,
compare_df=project_df,
base_name=benchmark_name,
compare_name=project_name,
comparison_type=ComparisonType.BENCHMARK
)
def version_comparison(self,
versions: List[Tuple[str, pd.DataFrame]]) -> List[ComparisonResult]:
"""Compare sequential versions."""
results = []
for i in range(1, len(versions)):
prev_name, prev_df = versions[i-1]
curr_name, curr_df = versions[i]
result = self.compare_estimates(
base_df=prev_df,
compare_df=curr_df,
base_name=prev_name,
compare_name=curr_name,
comparison_type=ComparisonType.VERSION
)
results.append(result)
return results
def export_comparison(self,
result: ComparisonResult,
output_path: str) -> str:
"""Export comparison to Excel."""
with pd.ExcelWriter(output_path, engine='openpyxl') as writer:
# Summary
summary_df = pd.DataFrame([{
'Comparison Type': result.comparison_type.value,
'Base': result.base_name,
'Compare': result.compare_name,
'Base Total': result.base_total,
'Compare Total': result.compare_total,
'Variance': result.total_variance,
'Variance %': result.total_variance_pct,
'Generated': result.created_at.strftime('%Y-%m-%d %H:%M')
}])
summary_df.to_excel(writer, sheet_name='Summary', index=False)
# Details
details_df = pd.DataFrame([
{
'Work Item': i.work_item_code,
'Description': i.description,
f'{result.base_name} Qty': i.base_quantity,
f'{result.base_name} Cost': i.base_cost,
f'{result.compare_name} Qty': i.compare_quantity,
f'{result.compare_name} Cost': i.compare_cost,
'Qty Variance': i.quantity_variance,
'Qty Variance %': i.quantity_variance_pct,
'Cost Variance': i.cost_variance,
'Cost Variance %': i.cost_variance_pct,
'Significance': i.significance.value
}
for i in result.items
])
details_df.to_excel(writer, sheet_name='Details', index=False)
# By Category
cat_df = pd.DataFrame([
{
'Category': cat,
'Base Cost': data['base_cost'],
'Compare Cost': data['compare_cost'],
'Variance': data['variance'],
'Variance %': data['variance_pct'],
'Items': data['item_count']
}
for cat, data in result.summary_by_category.items()
])
cat_df.to_excel(writer, sheet_name='By Category', index=False)
# Significant Variances
significant = self.get_significant_variances(result)
sig_df = pd.DataFrame([
{
'Work Item': i.work_item_code,
'Description': i.description,
'Cost Variance': i.cost_variance,
'Variance %': i.cost_variance_pct,
'Significance': i.significance.value
}
for i in significant
])
sig_df.to_excel(writer, sheet_name='Significant', index=False)
return output_path
class ComparisonAnalytics:
"""Analytics for comparison results."""
def __init__(self, comparison_tool: CWICRComparisonTool):
self.tool = comparison_tool
def variance_distribution(self, result: ComparisonResult) -> Dict[str, int]:
"""Get distribution of variance significance."""
distribution = {s.value: 0 for s in VarianceSignificance}
for item in result.items:
distribution[item.significance.value] += 1
return distribution
def top_variances(self,
result: ComparisonResult,
n: int = 10,
positive: bool = True) -> List[ComparisonItem]:
"""Get top N variances (positive or negative)."""
if positive:
sorted_items = sorted(result.items, key=lambda x: x.cost_variance, reverse=True)
else:
sorted_items = sorted(result.items, key=lambda x: x.cost_variance)
return sorted_items[:n]
def category_impact(self, result: ComparisonResult) -> pd.DataFrame:
"""Analyze which categories contribute most to variance."""
data = []
for cat, values in result.summary_by_category.items():
contribution_pct = (values['variance'] / result.total_variance * 100) if result.total_variance != 0 else 0
data.append({
'Category': cat,
'Variance': values['variance'],
'Contribution %': round(contribution_pct, 1)
})
return pd.DataFrame(data).sort_values('Contribution %', ascending=False)
def trend_analysis(self,
version_results: List[ComparisonResult]) -> pd.DataFrame:
"""Analyze cost trend across versions."""
data = []
cumulative = 0
for result in version_results:
cumulative += result.total_variance
data.append({
'From': result.base_name,
'To': result.compare_name,
'Variance': result.total_variance,
'Variance %': result.total_variance_pct,
'Cumulative Variance': cumulative
})
return pd.DataFrame(data)Quick Start
# Initialize comparison tool
tool = CWICRComparisonTool()
# Compare two estimate versions
result = tool.compare_estimates(
base_df=estimate_v1,
compare_df=estimate_v2,
base_name="Estimate v1.0",
compare_name="Estimate v2.0"
)
print(f"Total Variance: ${result.total_variance:,.2f} ({result.total_variance_pct}%)")Common Use Cases
1. Significant Variances
significant = tool.get_significant_variances(result)
for item in significant[:5]:
print(f"{item.work_item_code}: ${item.cost_variance:,.2f} ({item.significance.value})")2. Version History
versions = [
("v1.0", estimate_v1),
("v2.0", estimate_v2),
("v3.0", estimate_v3)
]
version_results = tool.version_comparison(versions)
analytics = ComparisonAnalytics(tool)
trend = analytics.trend_analysis(version_results)3. Design Alternatives
alternatives = [
("Option A - Steel", option_a),
("Option B - Concrete", option_b),
("Option C - Hybrid", option_c)
]
comparisons = tool.compare_multiple(alternatives, base_index=0)4. Export Report
tool.export_comparison(result, "estimate_comparison.xlsx")Resources
- GitHub: OpenConstructionEstimate-DDC-CWICR
- DDC Book: Chapter 3.1 - Estimate Management