pySODM 0.2.2

Simulating and Optimising Dynamical Models

pySODM

Simulating and Optimising Dynamical Models in Python 3

Links

Documentation: https://twallema.github.io/pySODM

Manuscript: https://arxiv.org/abs/2301.10664

Aim & Scope

A modeling and simulation workflow will typically constitute the following steps (see Villaverde et. al),

1. Build a system dynamical model to describe some real-world phenomenon. Assess structural identifiability.
2. Calibrate the model to a set of experimental data.
3. Extract knowledge from the calibrated parameter values (assess practical identifiability).
4. Use the model to make projections outside the calibrated range.

The aim of pySODM is to reduce the time it takes to step through this workflow. pySODM is a template to construct, simulate and calibrate dynamical systems governed by differential equations. Models can have n-dimensional labeled states of different sizes and can be simulated deterministically and stochastically. Model parameters can be time-dependent by means of complex functions with arbitrary inputs. The labeled n-dimensional model states can be aligned with n-dimensional data to compute the posterior probability function, which can subsequently be optimised.

Overview of features

Workflow	Features
Building a model	Solve coupled systems of equations deterministically (integration) or stochastically (Gillespie's SSA and Tau-Leaping)
	n-Dimensional model states with coordinates. Different states can have different sizes.
	Easy indexing, manipulating, saving, and piping to third-party software of model output by formatting simulation output as xarray.Dataset
Simulating a model	Vary model parameters during the simulation in accordance with an arbitrarily complex function containing any input
	Use draw functions to perform repeated simulations for sensitivity analysis. With multiprocessing support
Calibrating a model	Calibration of n-dimensional model parameters
	Construct a posterior probability function
	Automatic alignment of data and model prediction over timesteps and dimensions
	Nelder-Mead Simplex and Particle Swarm Optimization for frequentist optimization
	Pipeline to and backend for emcee.EnsembleSampler to perform Bayesian inference of model parameters
	Analysis of the mean-variance ratio in count-based datasets to aid in the choice of an appropriate likelihood function

Getting started

The quistart tutorial will teach you the basics of building and simulating models with n-dimensional labeled states in pySODM. It will demonstrate how to vary model parameters over the course of a simulation and how to perform repeated simulations with sampling of model parameters.

The workflow tutorial provides a step-by-step introduction to a modeling and simulation workflow by inferring the distributions of the model parameters of a simple compartmental disease model using a synthetic dataset.

The enzyme kinetics and influenza 17-18 case studies apply the modeling and simulation workflow to more advanced, real-world problems. In the enzyme kinetics case study, a 1D packed-bed reactor model is implemented in pySODM by reducing the two PDEs to a set of coupled ODEs by using the method-of-lines. In the Influenza 17-18 case study, a stochastic, age-structured model for influenza is developped and calibrated to the Influenza incidence data reported by the Belgian Federal Institute of Public Health. These case studies mainly serve to demonstrate pySODM's capabilities across scientific disciplines and highlight the arbitrarily complex nature of the models that can be built with pySODM. For an academic description of pySODM and on the Enzyme Kinetics and Influenza 17-18 case studies, checkout our manuscript.

Versions

• Version 0.2.0 (2023-01-19, PR #25)

  Introduction of state_dimensions in model declaration, allowing the user to define models where states can have different sizes.

  • Version 0.2.1 (2023-01-27, PR #30)

    Fixed bugs when using pySODM for the COVID-19 related models. More thorough checks on bounds in the log posterior probability function. Finished manuscript.

• Version 0.1 (2022-12-23, PR #14)

  Application pySODM to three use cases. Documentation website. Unit tests for ODEModel, SDEModel and calibration.

  • Version 0.1.1 (2023-01-09, PR #20)

    Start of semantic versions: Major.Minor.Patch

  • Version 0.1.2 (2023-01-11, PR #23)

    Calibration of 1-D model parameters generalized to n-dimensions. Added 'aggregation functions' to the log_posterior_probability class to perform custom aggregations of model output before matching with data. xarray.DataArray/xarray.Dataset can be used as datasets during calibration. Internally converted to pd.DataFrame.

• Version 0.0 (2022-11-14)
  • First pySODM version. Obtained by splitting the generally applicable parts from the ad-hoc parts in UGentBiomath/COVID19-Model. Without documentation website.
• Pre-development (2020-05-01 - 2022-11-24)
  • Code developped to model the spread of SARS-CoV-2 in Belgium (UGentBiomath/COVID19-Model).