pycmtensor 1.0.2

Python Tensor based package for Deep neural net assisted Discrete Choice Modelling.

PyCMTensor

A tensor-based choice modelling Python package with deep learning capabilities. Read the documentation at https://pycmtensor.readthedocs.io

About PyCMTensor

PyCMTensor is a discrete choice model development platform which is designed with the use of deep learning in mind, enabling users to write more complex models using neural networks. PyCMTensor is build on Aesara library, and uses many features commonly found in deep learning packages such as Tensorflow and Keras. Aesara was chosen as the back end mathematical library because of its hackable, open-source nature. As users of Biogeme, you will be familiar with the syntax of PyCMTensor.

This package allows one to incorporate neural networks into discrete choice models that boosts accuracy of model estimates which still being able to produce all the same statistical analysis found in traditional choice modelling software.

PyCMTensor aims to provide developers and researchers with deep learning tools for econometric and travel behaviour modelling with reproducible and interpretable results.

PyCMTensor and Biogeme

PyCMTensor improves on Biogeme in situations where much more complex models are necessary, for example, integrating neural networks into discrete choice models. PyCMTensor also include the ability to estimate models using 1st order stochastic gradient descent methods by default, such as Nesterov Accelerated Gradient, Adam, or RMSProp.

Features

• Estimate complex choice models with neural networks using deep learning algorithms
• Combines traditional econometric models (e.g. Multinomial Logit) with deep learning models (ResNets)
• Shares similar programming syntax with Biogeme, allowing easy transition between Biogeme and PyCMTensor methods
• Uses tensor based mathematical operations from the advanced features found in the Aesara library

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Pre-install

To install PyCMTensor, you need Conda (Full Anaconda works fine, but miniconda is recommmended for a minimal installation). Ensure that Conda is using at least Python 3.9.

Once Conda is installed, install the required dependencies from conda by running the following command in your terminal:

Windows

conda install pip git conda-forge::cxx-compiler conda-forge::libpython blas mkl-service numpy

Linux/MacOS

conda install blas mkl-service conda-forge::cxx-compiler

Note: MacOS user should also install Clang for a fast compiled code.

Install PyCMTensor

Then, run this command in your terminal to download and install the latest branch of PyCMTensor from PyPI:

pip install pycmtensor -U

Optional: If you want the development version from the Github repository:

pip install git+https://github.com/mwong009/pycmtensor.git@develop -U

The development branch is the most recent update of PyCMTensor. If you want a stable branch (master), remove @develop at the end of the .git url.

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How to use

PyCMTensor uses syntax very similar to Biogeme. Users of Biogeme should be familiar with the syntax.

Start an interactive session (IPython or Jupyter Notebook) and import:

import pycmtensor as cmt

Several submodules are also important to include:

from pycmtensor.expressions import Beta # Beta class for model parameters
from pycmtensor.models import MNLogit   # model library
from pycmtensor.optimizers import Adam  # Optimizers
from pycmtensor.results import Results  # for generating results

For a full list of submodules and description, refer to API Reference

Simple example: Swissmetro dataset

Using the swissmetro dataset from Biogeme, we define a simple MNL model.

Note:The following is a replication of the results from Biogeme using the Adam optimization algorithm. For further examples including the ResLogit model, refer here.

1. Import the dataset and perform some data santiation

   swissmetro = pd.read_csv("swissmetro.dat", sep="\t")
   db = cmt.Database(name="swissmetro", pandasDatabase=swissmetro, choiceVar="CHOICE")
   globals().update(db.variables)
   # additional steps to format database
   db.data["CHOICE"] -= 1 # set the first choice to 0
   db.choices = sorted(db.data["CHOICE"].unique()) # save original choices
   db.autoscale(
   	variables=['TRAIN_CO', 'TRAIN_TT', 'CAR_CO', 'CAR_TT', 'SM_CO', 'SM_TT'], 
   	default=100., 
   ) # automatically scales features by 1/100.
   

   cmt.Database() loads the dataset and defines Tensor Variables automatically.

2. Initialize the model parameters

   b_cost = Beta("b_cost", 0.0, None, None, 0)
   b_time = Beta("b_time", 0.0, None, None, 0)
   asc_train = Beta("asc_train", 0.0, None, None, 0)
   asc_car = Beta("asc_car", 0.0, None, None, 0)
   asc_sm = Beta("asc_sm", 0.0, None, None, 1)  # set to 1 to keep it fixed
   

3. Specify the utility functions and availability conditions

   U_1 = b_cost * db["TRAIN_CO"] + b_time * db["TRAIN_TT"] + asc_train
   U_2 = b_cost * db["SM_CO"] + b_time * db["SM_TT"] + asc_sm
   U_3 = b_cost * db["CAR_CO"] + b_time * db["CAR_TT"] + asc_car
   U = [U_1, U_2, U_3]
   AV = [db["TRAIN_AV"], db["SM_AV"], db["CAR_AV"]]
   

4. Specify the model MNLogit

   mymodel = MNLogit(u=U, av=AV, database=db, name="mymodel")
   mymodel.add_params(locals())  # load Betas into the model
   

5. Define the training hyperparameters

   mymodel.config["patience"] = 20000
   mymodel.config["max_epoch"] = 499
   mymodel.config["base_lr"] = 0.0012
   mymodel.config["max_lr"] = 0.002
   mymodel.config["learning_scheduler"] = "CyclicLR"
   mymodel.config["cyclic_lr_step_size"] = 8
   mymodel.config["cyclic_lr_mode"] = "triangular2"
   

6. Call the training function and save the trained model

   model = cmt.train(mymodel, database=db, optimizer=Adam)  # we use the Adam Optimizer
   

7. Generate the statistics and correlation matrices

   result = Results(model, db, show_weights=True)
   result.print_beta_statistics()
   result.print_correlation_matrix()
   

   Sample output:

    Optimization complete with accuracy of 62.618%. Max loglikelihood reached @ epoch 195.	
   
    Results for model: mymodel
    Build time: 00:00:13
    Estimation time: 00:00:28
    Estimation rate: 13.781 epochs/s
    Seed value: 999
    Number of Beta parameters: 4
    Sample size: 6768
    Excluded data: 3960
    Init loglikelihood: -6964.663
    Final loglikelihood: -5590.672
    Final loglikelihood reached at: epoch 195
    Likelihood ratio test: 2747.982
    Accuracy: 62.618%
    Rho square: 0.197
    Rho bar square: 0.197
    Akaike Information Criterion: 11189.34
    Bayesian Information Criterion: 11216.62
    Final gradient norm: 0.111
   
    Statistical Analysis:
                  Value   Std err     t-test   p-value Rob. Std err Rob. t-test Rob. p-value
    asc_car    0.111877  0.042071   2.659267  0.007831     0.038512    2.905005     0.003672
    asc_train -0.624174   0.05471 -11.408845       0.0     0.014402   -43.33787          0.0
    b_cost     0.002601  0.002547    1.02136  0.307084     0.003616    0.719242     0.471992
    b_time     -1.16109  0.054086 -21.467576       0.0     0.005372 -216.155293          0.0
   
    Correlation matrix:
                 b_cost    b_time  asc_train   asc_car
    b_cost     1.000000 -0.105761   0.154368  0.283711
    b_time    -0.105761  1.000000  -0.724388 -0.659056
    asc_train  0.154368 -0.724388   1.000000  0.606882
    asc_car    0.283711 -0.659056   0.606882  1.000000
   

8. Plot the training performance and accuracy

   

9. Compute the elasticities

   

10. Visualize the computation graph

    import aesara.d3viz as d3v
    from aesara import printing
    printing.pydotprint(mymodel.cost, "graph.png")
    

    

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Credits

PyCMTensor was inspired by Biogeme and aims to provide deep learning modelling tools for transport modellers and researchers.

This package was generated with Cookiecutter and the audreyr/cookiecutter-pypackage project template.