IGLU_PYTHON library

Concept

IGLU_PYTHON is a pure Python implementation of the widely-used IGLU (Interpreting GLUcose data) package. While the original IGLU implementation (referred to as iglu-r) is highly regarded in the research community, its R-based implementation has limited its adoption outside academic settings. The existing IGLU-PY solution provides a Python-to-R bridge but still requires a complete R installation and its dependencies.

IGLU_PYTHON reimplements all IGLU metric functions natively in Python, eliminating the need for R while maintaining full compatibility with the original package.

This project is proudly sponsored by Pheno.AI.

IGLU-R Compatibility

A significant focus of this project has been ensuring compatibility with the original R implementation of IGLU. To achieve this:

• The test suite includes validation against the original R implementation
• Test data is generated using tests/build_expected_values.py, which interfaces with the R implementation through an iglu-py adaptation layer
• Expected results are stored in tests/expected_results.json
• Each unit test in the package compares Python implementation results against the R-generated reference values

This approach ensures that the Python implementation produces results consistent with the original R package.

Input & Output

The implementation maintains compatibility with the R version while following Python best practices. The metrics can be used as:

import iglu_python ias iglu

# With DataFrame input
result_df = iglu.cv_glu(data)  # data should have 'id', 'time', and 'gl' columns
# Return DataFrame with "id' and column(s) with value(s)

# With Series input (some metrics require Series with DateTimeIndex)
result_float = iglu.cv_glu(glucose_series)  # just glucose values
# returns a single float value

# Same with function that support list or ndarray
result_float = iglu.cv_glu(glucose_list)  # list of glucose values
# returns a single float value

IGLU-R Compatibility Test Status

The current version of IGLU-PYTHON is test-compatible with IGLU-R v4.3.0 (2025-07-12)

Unless noted, IGLU-R test compatability is considered successful if it achieves precision of 0.001

Function	Description	IGLU-R test compatibility	list /ndarray /Series input	TZ	Comments
above_percent	percentage of values above target thresholds	✅	✅ returns Dict[str,float]
active_percent	percentage of time CGM was active	✅	✅ only Series(DatetimeIndex) returns Dict[str,float]
adrr	average daily risk range	✅	✅ only Series(DatetimeIndex) returns float
auc	Area Under Curve	🟡 (0.01 precision)	✅ only Series(DatetimeIndex) returns float		see auc_evaluation.ipynb
below_percent	percentage of values below target thresholds	✅	✅ returns Dict[str,float]
cogi	Coefficient of Glucose Irregularity	✅	✅ returns float
conga	Continuous Overall Net Glycemic Action	✅	✅ only Series(DatetimeIndex) returns float
cv_glu	Coefficient of Variation	✅	✅ returns float
cv_measures	Coefficient of Variation subtypes (CVmean and CVsd)	✅	✅ only Series(DatetimeIndex) returns Dict[str,float]
ea1c	estimated A1C (eA1C) values	✅	✅ returns float
episode_calculation	Hypo/Hyperglycemic episodes with summary statistics	✅	🟡 always returns DataFrame(s)
gmi	Glucose Management Indicator	✅	✅ returns float
grade_eugly	percentage of GRADE score attributable to target range	✅	✅ returns float
grade_hyper	percentage of GRADE score attributable to hyperglycemia	✅	✅ returns float
grade_hypo	percentage of GRADE score attributable to hypoglycemia	✅	✅ returns float
grade	mean GRADE score	✅	✅ returns float
gri	Glycemia Risk Index	✅	✅ returns float
gvp	Glucose Variability Percentage	✅	✅ only Series(DatetimeIndex) returns float
hbgi	High Blood Glucose Index	✅	✅ returns float
hyper_index	Hyperglycemia Index	✅	✅ returns float
hypo_index	Hypoglycemia Index	✅	✅ returns float
igc	Index of Glycemic Control	✅	✅ returns float
in_range_percent	percentage of values within target ranges	✅	✅ returns Dict[str,float]
iqr_glu	glucose level interquartile range	✅	✅ returns float
j_index	J-Index score for glucose measurements	✅	✅ returns float
lbgi	Low Blood Glucose Index	✅	✅ returns float
m_value	M-value of Schlichtkrull et al	✅	✅ returns float
mad_glu	Median Absolute Deviation	✅	✅ returns float
mag	Mean Absolute Glucose	✅	✅ only Series(DatetimeIndex) returns float
mage	Mean Amplitude of Glycemic Excursions	✅	✅ only Series(DatetimeIndex) returns float		See algorithm at MAGE
mean_glu	Mean glucose value	✅	✅ returns float
median_glu	Median glucose value	✅	✅ returns float
modd	Mean of Daily Differences	✅	✅ only Series(DatetimeIndex) returns float
pgs	Personal Glycemic State	✅	✅ only Series(DatetimeIndex) returns float
quantile_glu	glucose level quantiles	✅	✅ returns List[float]
range_glu	glucose level range	✅	✅ returns float
roc	Rate of Change	✅	🟡 always returns DataFrame
sd_glu	standard deviation of glucose values	✅	✅ returns float
sd_measures	various standard deviation subtypes	✅	✅ only Series(DatetimeIndex) returns Dict[str,float]
sd_roc	standard deviation of the rate of change	✅	✅ only Series(DatetimeIndex) returns float
summary_glu	summary glucose level	✅	✅ returns Dict[str,float]
process_data	Data Pre-Processor	✅
CGMS2DayByDay	Interpolate glucose input	✅

Extended functionality

IGLU_PYTHON extends beyond the capabilities of the original IGLU-R package by offering enhanced functionality and improved user experience. We believe that combining these extended features with the proven reliability of IGLU-R creates a powerful synergy that benefits both the research community and wide software developers community.

Function	Description
LOAD DATA FROM DEVICE SPECIFIC FILE
load_libre()	Load Timeseries from Libre device file (CGM reading converted into mg/dL)
load_dexcom()	Load Timeseries from Dexcom device file (CGM reading converted into mg/dL)
**PLOT/VISUALISE CGM **
plot_daily()	Plot daily Glucose values for each day
plot_statistics()	Plot median + quantile daily statistics

Installation

Install IGLU_PYTHON using pip:

pip install iglu-python

For development installation:

git clone https://github.com/staskh/iglu_python.git
cd iglu_python
pip install -e .

Examples of Use

Basic Usage with DataFrame

import pandas as pd
import iglu_python as iglu

# Load your glucose data into a DataFrame
# Expected columns: 'id' (subject identifier) and 'gl' (glucose values)
# Optional: datetime index or 'time' column
data = pd.DataFrame({
    'id': ['Subject1'] * 100,
    'time': pd.date_range(start='2023-01-01', periods=100, freq='5min'),
    'gl': [120, 135, 140, 125, 110]*20  # glucose values in mg/dL
})

# Calculate glucose metrics
mean_glucose = iglu.mean_glu(data)
cv = iglu.cv_glu(data)
active = iglu.active_percent(data)

print(f"Mean glucose: {mean_glucose['mean'][0]}")
print(f"CV: {cv['CV'][0]}")
print(f"CGM active percent: {active['active_percent'][0]}%")

Using with Time Series Data

import pandas as pd
import numpy as np
import iglu_python as iglu

# Create time series data
timestamps = pd.date_range(start='2023-01-01', periods=288, freq='5min')
glucose_values = [120 + 20 * np.sin(i/48) + np.random.normal(0, 5) for i in range(288)]

data = pd.Series(glucose_values, index=timestamps)

# Calculate advanced metrics
mage = iglu.mage(data)
auc = iglu.auc(data)
gmi = iglu.gmi(data)

print(f"MAGE: {mage}")
print(f"AUC: {auc}")
print(f"GMI: {gmi}")

Multiple Input Formats

(Not yet fully implemented and tested)

import iglu_python as iglu
import numpy as np

# Using list (assumes 5-minute intervals)
glucose_list = [120, 135, 140, 125, 110, 95, 105, 115]
mean_from_list = iglu.mean_glu(glucose_list)

# Using NumPy array
glucose_array = np.array([120, 135, 140, 125, 110, 95, 105, 115])
cv_from_array = iglu.cv_glu(glucose_array)

# Using Pandas Series with DatetimeIndex
glucose_series = pd.Series(
    data=[120, 135, 140, 125, 110, 95, 105, 115],
    index=pd.date_range(start='2023-01-01', periods=8, freq='5min')
)
sd_from_series = iglu.sd_glu(glucose_series)

Notes on IGLU-R Compatibility

During our implementation and testing process, we identified several discrepancies between our Python implementation and the original R version of IGLU. While maintaining test compatibility remains a priority, we are actively working with the IGLU-R development team to investigate and resolve these issues.

Known Implementation Differences

Timezone Handling in check_data_columns

The function's timezone handling behavior requires clarification:

• When a specific timezone is provided, the function performs a timezone conversion (tz_convert) rather than timezone localization (tz_localize)
• This means timestamps are being transformed to the target timezone instead of being labeled with it
• The intended behavior needs to be confirmed with the original IGLU-R authors
• This difference in timezone handling may affect daily aggregation and analysis results

CGMS2DayByDay Function

The following issues have been identified in the R implementation:

1. Timezone Handling:

   • When using tz=UTC, data points are shifted one day earlier than expected
   • Status: Pending test case development to demonstrate the issue

2. Grid Alignment:

   • Results are shifted one grid index to the left from the expected values
   • Status: Pending test case development to demonstrate the issue

We are maintaining test compatibility while these issues are being investigated. Updates will be provided as we receive clarification from the IGLU-R development team.

Input Data Types

Most metric functions, in addition to a standard DataFrame, support multiple input formats for glucose readings:

• List[float]: Python list of glucose values
• np.array: NumPy array of glucose values
• pd.Series: Pandas Series of glucose values (with or without DatetimeIndex)

When using these sequence types (without timestamps), the functions assume a fixed 5-minute interval between measurements. For more precise analysis with variable time intervals, use the DataFrame input format with explicit timestamps or Series with DatetimeIndex .

ToDo

• implement Series/list/array as an input for all metrics (suing Series with DatetimeIndex)
• optimize code by NOT converting arrays/Series into DataFrames
• test and implement tz='UTC' timezone assignment
• clarify functionality correctness for CGMS2DayByDay