biosignal-quality 0.1.1

A toolkit for analyzing, assessing, and visualizing biosignal quality

BioSignal Quality Analysis

A comprehensive toolkit for analyzing, visualizing, and evaluating the quality of physiological time series signals such as PPG (photoplethysmography) and ECG (electrocardiography).

Screenshots

DashBoard

Report

Features

• Quality Assessment: Evaluate quality using cross-correlation with shifted segments
• Interactive Dashboard: Visual exploration of signal segments with real-time quality metrics
• Quality Reporting: Generate comprehensive HTML reports with visualizations
• Segment Processing: Prepare and analyze segments with appropriate padding to avoid edge effects

How It Works

The library assesses signal quality based on the periodicity of waveforms. For physiological signals like PPG and ECG, we expect a repetitive pattern corresponding to heart rate (typically 40-120 BPM or 0.5-1.5 seconds between peaks).

Methodology:

1. Segment Processing: Signal is broken into segments of fixed duration
2. Cleaning: Signal is cleaned using specialized functions (e.g., nk.ppg_clean() for PPG data)
3. Autocorrelation Analysis: The cleaned signal is correlated with time-shifted versions of itself
4. Quality Assessment: Maximum correlation within the expected heart rate range determines quality
5. Visual Feedback: Interactive plots or reports show raw vs. cleaned signals and correlation patterns

Installation

pip install biosignal-quality

Core Functions

The library provides three main functions:

1. assess_quality

Analyzes signal segments and returns a DataFrame with timestamps and quality scores.

from biosignal_quality import assess_quality
import pandas as pd
import neurokit2 as nk

# Load your signal data
data = pd.read_csv("your_signal_data.csv")

# Get quality scores for each segment
quality_df = assess_quality(
    df=data,
    signal_col="ppg_signal",
    clean_func=nk.ppg_clean,
    sampling_rate=186,
    step_size_sec=1,
    segment_duration_sec=10
)

# Result includes timestamps and quality scores (0-1)
print(quality_df.head())

2. assess_quality_percentage

Provides an overall quality assessment with optional HTML report generation.

from biosignal_quality import assess_quality_percentage
import neurokit2 as nk

# Get percentage of high-quality segments and generate HTML report
quality_percentage = assess_quality_percentage(
    df=data,
    signal_col="ecg_signal",
    clean_func=nk.ecg_clean,
    sampling_rate=200,
    quality_threshold=0.6,
    plot="ecg_quality_report.html"  # Optional: generate HTML report
)

print(f"Recording quality: {quality_percentage:.1f}% high-quality segments")

3. signal_quality_dashboard

Launches an interactive dashboard for exploring signal quality.

from biosignal_quality import signal_quality_dashboard
import neurokit2 as nk

# Define optional normalization function
def zscore_normalize(signal):
    import numpy as np
    return (signal - np.mean(signal)) / np.std(signal)

# Launch interactive dashboard
signal_quality_dashboard(
    df=data,
    signal_col="ppg_signal",
    clean_func=nk.ppg_clean,
    normalize_func=zscore_normalize,
    signal_label="PPG",
    sampling_rate=186
)

Parameter Reference

Parameter	Description	Default
df	DataFrame containing the signal with a 'time' column	-
signal_col	Column name containing the signal	-
clean_func	Function to clean the signal (e.g., nk.ppg_clean)	-
signal_label	Label for the signal in visualizations	"Signal"
normalize_func	Optional function to normalize signals	None
sampling_rate	Sampling rate in Hz	186
segment_duration_sec	Duration of segment in seconds	10
step_size_sec	Step size between segments for assessment	1
quality_lag_low	Lower bound for quality assessment lag (seconds)	0.5
quality_lag_high	Upper bound for quality assessment lag (seconds)	1.5
quality_threshold	Threshold for determining high-quality segments	0.6
max_lag_sec	Maximum lag in seconds for autocorrelation	3
clean_padding_ratio	Ratio of padding to add before cleaning	0.2
delta_padding_sec	Additional padding in seconds for extended segment	1.6
plot	Path to save HTML report (for assess_quality_percentage)	None
bin_size	Bin size for quality score histogram in report	0.1
num_plots_bin	Number of example segments to plot per quality bin	1
launch_dashboard	Whether to launch interactive dashboard	False
verbose	Whether to print progress information	False

Example: Complete Analysis Workflow

import pandas as pd
import numpy as np
import neurokit2 as nk
from biosignal_quality import assess_quality, assess_quality_percentage, signal_quality_dashboard

# Load data
data = pd.read_csv("ppg_recording.csv")

# Define normalization function
def zscore_normalize(signal):
    return (signal - np.mean(signal)) / np.std(signal)

# Step 1: Get quick overall quality assessment with report
quality_pct = assess_quality_percentage(
    df=data,
    signal_col="ppg",
    clean_func=nk.ppg_clean,
    sampling_rate=186,
    quality_threshold=0.6,
    plot="quality_report.html",
    signal_label="PPG"
)
print(f"Overall signal quality: {quality_pct:.1f}%")

# Step 2: Get detailed quality scores for each segment
quality_df = assess_quality(
    df=data,
    signal_col="ppg",
    clean_func=nk.ppg_clean,
    sampling_rate=186,
    step_size_sec=1
)

# Step 3: Find segments with best and worst quality
best_segments = quality_df.nlargest(5, 'quality_score')
worst_segments = quality_df.nsmallest(5, 'quality_score')

# Step 4: Launch interactive dashboard to explore specific segments
signal_quality_dashboard(
    df=data,
    signal_col="ppg",
    clean_func=nk.ppg_clean,
    normalize_func=zscore_normalize,
    sampling_rate=186,
    signal_label="PPG"
)

HTML Report Contents

When generating a quality report using assess_quality_percentage() with the plot parameter, the HTML report includes:

• Summary Statistics: Overall quality percentage and distribution
• Quality Timeline: Heatmap showing quality scores over time
• Quality Histogram: Distribution of quality scores
• Example Segments: Representative segments for different quality levels
• Autocorrelation Plots: Correlation patterns for selected segments

Dashboard Controls

The interactive dashboard provided by signal_quality_dashboard() includes:

• Segment Navigation: Navigate through signal segments
• Raw/Cleaned Signal Toggle: Compare raw and processed signals
• Normalization Option: Apply normalization to the displayed signals
• Quality Threshold Adjustment: Set the correlation threshold for "good" quality
• Quality Search: Find segments meeting the quality threshold criteria
• Auto-correlation Analysis: Visualize signal periodicity at different lags

License

MIT License