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Tutorial 4b: Parameter Introspection and Comparison

This tutorial introduces the parameter introspection features in PyBaMM’s ParameterValues class. These features help you:

1. Understand parameters - Get metadata like units and categories

2. Browse by category - Find parameters related to electrodes, thermal, etc.

3. Compare parameter sets - See differences between parameter sets

import pybamm

pybamm.set_logging_level("WARNING")

1. Getting Parameter Information

The get_info() method returns metadata about a parameter including its value, units, and category.

# Load the Chen2020 parameter set
params = pybamm.ParameterValues("Chen2020")

# Get information about a specific parameter
info = params.get_info("Maximum concentration in negative electrode [mol.m-3]")

print(f"Parameter: {info.name}")
print(f"Value: {info.value}")
print(f"Units: {info.units}")
print(f"Category: {info.category}")
print(f"Is function: {info.is_function}")
print(f"Is input parameter: {info.is_input}")

Parameter: Maximum concentration in negative electrode [mol.m-3]
Value: 33133.0
Units: mol.m-3
Category: negative electrode
Is function: False
Is input parameter: False

2. Browsing Parameters by Category

Use list_by_category() to find all parameters in a specific category, or categories() to see all parameters grouped by category.

# List all negative electrode parameters
neg_electrode_params = params.list_by_category("negative electrode")
print(f"Found {len(neg_electrode_params)} negative electrode parameters:")
for p in neg_electrode_params[:5]:  # Show first 5
    print(f"  - {p}")
print("  ...")

Found 19 negative electrode parameters:
  - Negative electrode reaction-driven LAM factor [m3.mol-1]
  - Negative electrode thickness [m]
  - Negative electrode conductivity [S.m-1]
  - Maximum concentration in negative electrode [mol.m-3]
  - Negative particle diffusivity [m2.s-1]
  ...

# Get all categories and their counts
all_categories = params.categories()
print("Parameters by category:")
for category, param_list in all_categories.items():
    print(f"  {category}: {len(param_list)} parameters")

Parameters by category:
  other: 14 parameters
  geometric: 7 parameters
  kinetic: 2 parameters
  thermal: 13 parameters
  electrolyte: 4 parameters
  negative electrode: 19 parameters
  positive electrode: 19 parameters
  separator: 6 parameters
  electrical: 9 parameters

neg_electrode_params

['Negative electrode reaction-driven LAM factor [m3.mol-1]',
 'Negative electrode thickness [m]',
 'Negative electrode conductivity [S.m-1]',
 'Maximum concentration in negative electrode [mol.m-3]',
 'Negative particle diffusivity [m2.s-1]',
 'Negative electrode OCP [V]',
 'Negative electrode porosity',
 'Negative electrode active material volume fraction',
 'Negative particle radius [m]',
 'Negative electrode Bruggeman coefficient (electrolyte)',
 'Negative electrode Bruggeman coefficient (electrode)',
 'Negative electrode charge transfer coefficient',
 'Negative electrode double-layer capacity [F.m-2]',
 'Negative electrode exchange-current density [A.m-2]',
 'Negative electrode density [kg.m-3]',
 'Negative electrode specific heat capacity [J.kg-1.K-1]',
 'Negative electrode thermal conductivity [W.m-1.K-1]',
 'Negative electrode OCP entropic change [V.K-1]',
 'Initial concentration in negative electrode [mol.m-3]']

3. Comparing Parameter Sets

Use diff() to compare two parameter sets and see what’s different.

# Load another parameter set
chen = pybamm.ParameterValues("Chen2020")
marquis = pybamm.ParameterValues("Marquis2019")

# Compare them
diff = chen.diff(marquis)

print(f"Parameters only in Chen2020: {len(diff.removed)}")
print(f"Parameters only in Marquis2019: {len(diff.added)}")
print(f"Parameters with different values: {len(diff.changed)}")

Parameters only in Chen2020: 1
Parameters only in Marquis2019: 12
Parameters with different values: 46

# Show some changed parameters
print("\nSome parameters with different values:")
for key, (chen_val, marquis_val) in list(diff.changed.items())[:5]:
    if not callable(chen_val) and not callable(marquis_val):
        print(f"  {key}:")
        print(f"    Chen2020: {chen_val}")
        print(f"    Marquis2019: {marquis_val}")

Some parameters with different values:
  Positive electrode Bruggeman coefficient (electrode):
    Chen2020: 0
    Marquis2019: 1.5
  Current function [A]:
    Chen2020: 5.0
    Marquis2019: 0.680616
  Electrode width [m]:
    Chen2020: 1.58
    Marquis2019: 0.207