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74 lines
3.1 KiB
Python
74 lines
3.1 KiB
Python
import numpy as np
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class SinglespeedAnalyzer:
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def __init__(self):
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self.chainring_options = [38, 46] # teeth
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self.common_cogs = list(range(11, 28)) # 11t to 27t rear cogs
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self.wheel_circumference_m = 2.096 # 700x25c tire
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def analyze_gear_ratio(self, speed_data, cadence_data, gradient_data):
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"""Determine most likely singlespeed gear ratio"""
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# Validate input parameters
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if not speed_data or not cadence_data or not gradient_data:
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raise ValueError("Input data cannot be empty")
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if len(speed_data) != len(cadence_data) or len(speed_data) != len(gradient_data):
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raise ValueError("Input data arrays must be of equal length")
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# Filter for flat terrain segments (gradient < 3%)
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flat_indices = [i for i, grad in enumerate(gradient_data) if abs(grad) < 3.0]
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flat_speeds = [speed_data[i] for i in flat_indices]
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flat_cadences = [cadence_data[i] for i in flat_indices]
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# Only consider data points with sufficient speed (15 km/h) and cadence
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valid_indices = [i for i in range(len(flat_speeds))
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if flat_speeds[i] > 4.17 and flat_cadences[i] > 0] # 15 km/h threshold
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if not valid_indices:
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return None # Not enough data
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valid_speeds = [flat_speeds[i] for i in valid_indices]
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valid_cadences = [flat_cadences[i] for i in valid_indices]
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# Calculate gear ratios from speed and cadence
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gear_ratios = []
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for speed, cadence in zip(valid_speeds, valid_cadences):
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# Gear ratio = (speed in m/s * 60 seconds/minute) / (cadence in rpm * wheel circumference in meters)
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gr = (speed * 60) / (cadence * self.wheel_circumference_m)
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gear_ratios.append(gr)
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# Calculate average gear ratio
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avg_gear_ratio = sum(gear_ratios) / len(gear_ratios)
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# Find best matching chainring and cog combination
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best_fit = None
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min_diff = float('inf')
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for chainring in self.chainring_options:
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for cog in self.common_cogs:
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theoretical_ratio = chainring / cog
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diff = abs(theoretical_ratio - avg_gear_ratio)
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if diff < min_diff:
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min_diff = diff
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best_fit = (chainring, cog, theoretical_ratio)
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if not best_fit:
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return None
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chainring, cog, ratio = best_fit
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# Calculate gear metrics
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wheel_diameter_inches = 27.0 # 700c wheel diameter
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gear_inches = ratio * wheel_diameter_inches
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development_meters = ratio * self.wheel_circumference_m
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# Calculate confidence score (1 - relative error)
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confidence = max(0, 1 - (min_diff / ratio)) if ratio > 0 else 0
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return {
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'estimated_chainring_teeth': chainring,
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'estimated_cassette_teeth': cog,
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'gear_ratio': ratio,
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'gear_inches': gear_inches,
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'development_meters': development_meters,
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'confidence_score': confidence
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}
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