Signal Verification Examples

This page demonstrates how to use EMGIO's verification capabilities to ensure signal integrity when transferring EMG data between formats.

Basic Verification Workflow

from emgio import EMG
import matplotlib.pyplot as plt
from emgio.analysis.verification import compare_signals, report_verification_results

# Load original data from a device-specific format
emg_original = EMG.from_file('sample_data.csv', importer='trigno')
# just keep the EMG channels
emg_channels = [ch for ch, info in emg_original.channels.items() if info['channel_type'] == 'EMG']
emg_original = emg_original.select_channels(emg_channels)  # Creates a new EMG object with only EMG channels

# Export to EDF (automatically selects EDF or BDF based on signal characteristics)
emg_original.to_edf('exported_data')

# Reload the exported data
emg_reloaded = EMG.from_file('exported_data.edf')

# Verify signals using the verification module
results = compare_signals(emg_original, emg_reloaded, tolerance=0.01)
is_identical = report_verification_results(results, verify_tolerance=0.01)

print(f"Verification result: {'Passed' if is_identical else 'Failed'}")

Visual Comparison

The plot_comparison() function provides a visual way to compare signals:

from emgio.visualization.static import plot_comparison

# Visual comparison of original and reloaded signals
plot_comparison(emg_original, emg_reloaded, channels=['EMG1', 'EMG2'])
plt.show()

# Customize the comparison
plot_comparison(
    emg_original,
    emg_reloaded,
    channels=['EMG1', 'EMG2'],
    time_range=(0, 5),  # Only show first 5 seconds
    detrend=True,       # Remove mean for easier comparison
    grid=True           # Add grid lines
)
plt.show()

Detailed Verification Analysis

For more control and detailed analysis, you can use the verification module directly:

from emgio.analysis.verification import compare_signals, report_verification_results

# Compare with detailed metrics
results = compare_signals(
    emg_original,
    emg_reloaded,
    tolerance=0.01,  # Set custom tolerance (1%)
    channel_map=None  # Use automatic channel matching
)

# Generate detailed report
is_identical = report_verification_results(results, verify_tolerance=0.01)

# Inspect results for specific channels
print("\nDetailed metrics per channel:")
for channel, metrics in results.items():
    if channel != 'channel_summary':
        print(f"Channel: {channel}")
        print(f"  - NRMSE: {metrics['nrmse']:.6f}")
        print(f"  - Max Normalized Difference: {metrics['max_norm_abs_diff']:.6f}")
        print(f"  - Identical within tolerance: {metrics['is_identical']}")

Handling Channel Mapping

When channels are renamed during export/import:

from emgio.visualization.static import plot_comparison

# Define explicit channel mapping
channel_map = {
    'EMG_biceps': 'CH1',
    'EMG_triceps': 'CH2',
    'EMG_forearm': 'CH3'
}

# Compare with channel mapping
results = compare_signals(
    emg_original,
    emg_reloaded,
    tolerance=0.01,
    channel_map=channel_map
)

# Generate report with the mapping applied
is_identical = report_verification_results(results, verify_tolerance=0.01)

# Visual comparison with channel mapping
plot_comparison(
    emg_original,
    emg_reloaded,
    channel_map=channel_map,
    time_range=(0, 5)
)
plt.show()

Real-World Example: CSV to EDF Conversion

from emgio import EMG
import matplotlib.pyplot as plt
from emgio.analysis.verification import compare_signals, report_verification_results
from emgio.visualization.static import plot_comparison

# 1. Load original Trigno CSV data
emg_trigno = EMG.from_file('trigno_data.csv', importer='trigno')

# 2. Export to EDF
emg_trigno.to_edf('converted_data')
print(f"Data exported. Duration: {emg_trigno.get_duration():.2f}s, "
      f"Channels: {emg_trigno.get_n_channels()}")

# 3. Reload from EDF
emg_edf = EMG.from_file('converted_data.edf')
print(f"Data reloaded. Duration: {emg_edf.get_duration():.2f}s, "
      f"Channels: {emg_edf.get_n_channels()}")

# 4. Verification using the analysis module
results = compare_signals(emg_trigno, emg_edf, tolerance=0.01)
is_identical = report_verification_results(results, verify_tolerance=0.01)
print(f"Verification result: {'Passed' if is_identical else 'Failed'}")

# 5. Visual verification of a few channels
plt.figure(figsize=(14, 8))
plot_comparison(
    emg_trigno,
    emg_edf,
    channels=list(emg_trigno.signals.columns)[:3],  # First 3 channels
    time_range=(0, 2),  # First 2 seconds
    detrend=True
)
plt.suptitle("Trigno CSV to EDF Conversion Verification", fontsize=16)
plt.tight_layout(rect=[0, 0.03, 1, 0.95])
plt.show()