pycmtensor 1.3.1

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

PyCMTensor

A tensor-based discrete choice modelling Python package.

Citation

Cite as:

@software{melvin_wong_2022_7249280,
  author       = {Melvin Wong},
  title        = {mwong009/pycmtensor: v1.3.1},
  year         = 2022,
  version      = {v1.3.1},
  doi          = {10.5281/zenodo.7249280},
  url          = {https://doi.org/10.5281/zenodo.7249280}
}

Table of contents

• PyCMTensor
  • Citation
  • Table of contents
  • About PyCMTensor
  • Features
• Quick start
  • Installation
• Usage
  • Simple example: Swissmetro dataset
  • Results
• Development
  • Installing the virtual environment
  • Install the project and development dependencies

About PyCMTensor

PyCMTensor is a discrete choice modelling development tool on deep learning libraries, enabling development of complex models using deep neural networks. PyCMTensor is build on Aesara, a tensor library which uses 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. Users of Biogeme would be familiar with the syntax of PyCMTensor.

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 (NAG), Adaptive momentum (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 (e.g. ResNets)
• Shares similar programming syntax with Biogeme, allowing easy transition between models
• Uses tensor features found in the Aesara library

---

Quick start

Installation

1. Download and install Miniconda

   Full Anaconda works fine, but Miniconda is recommmended for a minimal installation. Ensure that Conda is using at least Python 3.9

   Next, install the required dependencies:

   Windows

   conda install mkl-service conda-forge::cxx-compiler conda-forge::m2w64-toolchain
   

   Linux

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

   Mac OSX

   conda install mkl-service Clang
   

2. Install the PyCMTensor package

   PyCMTensor is available on PyPi https://pypi.org/project/pycmtensor/. It can be installed with pip

   pip install -U pycmtensor==1.3.1
   

   Alternatively, the latest development version is available via Github. It can be installed via

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

For more information about installing, see Installation.

Usage

PyCMTensor uses syntax very similar to Biogeme. Users of Biogeme should be familiar with the syntax. Make sure you are using the correct Conda environment and/or the required packages are installed.

Simple example: Swissmetro dataset

1. Start an interactive session (e.g. IPython or Jupyter Notebook) and import the PyCMTensor package:

   import pycmtensor as cmt
   import pandas as pd
   

   Several submodules to include:

   from pycmtensor.expressions import Beta # Beta class for model parameters
   from pycmtensor.models import MNL  # MNL model
   from pycmtensor.statistics import elasticities  # For calculating elasticities
   

   For a full list of submodules and description, refer to API Reference. Using the swissmetro dataset, we define a simple MNL model.

:warning: Note: The following is a replication of the results from Biogeme using the Adam optimization method with constant learning rate.

1. Import the dataset and perform some data cleaning

   swissmetro = pd.read_csv("swissmetro.dat", sep="\t")
   swissmetro.drop(swissmetro[swissmetro["CHOICE"] == 0].index, inplace=True)
   swissmetro["CHOICE"] -= 1  # set the first choice index to 0
   db = cmt.Data(df=swissmetro, choice="CHOICE")
   db.autoscale_data(except_for=["ID", "ORIGIN", "DEST"])  # scales dataset
   db.split_db(split_frac=0.8)  # split dataset into train/valid sets
   

2. Initialize the model parameters and specify the utility functions and availability conditions

   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)
   
   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
   
   # specify the utility function and the availability conditions
   U = [U_1, U_2, U_3]  # utility
   AV = [db["TRAIN_AV"], db["SM_AV"], db["CAR_AV"]]  # availability
   

3. Define the Multinomial Logit model

   mymodel = MNL(db, locals(), U, AV, name="MNL")
   

4. Train the model and generate model statistics (Optionally, you can also set the training hyperparameters)

   mymodel.config.set_hyperparameter("max_steps", 200)  # set the max number of train steps
   mymodel.config.set_hyperparameter("batch_size", 128)  # set the training batch size
   mymodel.train(db)  # run the model training on the dataset `db`
   

Results

The following model functions outputs the statistics, results of the model, and model training

1. Model estimates

   print(mymodel.results.beta_statistics())
   

   Output:

                 value   std err     t-test   p-value rob. std err rob. t-test rob. p-value
   asc_car   -0.665638  0.044783 -14.863615       0.0     0.176178    -3.77821     0.000158
   asc_sm          0.0         -          -         -            -           -            -
   asc_train -1.646826  0.048099 -34.238218       0.0     0.198978   -8.276443          0.0
   b_cost     0.024912   0.01943   1.282135  0.199795     0.016413    1.517851     0.129052
   b_time    -0.313186  0.049708  -6.300485       0.0     0.208239   -1.503979     0.132587
   

2. Training results

   print(mymodel.results.model_statistics())
   

   Output:

                                             value
   Number of training samples used          8575.0
   Number of validation samples used        2143.0
   Init. log likelihood               -8874.438875
   Final log likelihood                -7513.22967
   Accuracy                                 59.26%
   Likelihood ratio test                2722.41841
   Rho square                             0.153385
   Rho square bar                         0.152822
   Akaike Information Criterion       15036.459339
   Bayesian Information Criterion      15071.74237
   Final gradient norm                    0.007164
   

3. Correlation matrix

   print(mymodel.results.model_correlation_matrix())
   

   Output:

                b_cost    b_time  asc_train   asc_car
   b_cost     1.000000  0.209979   0.226737 -0.028335
   b_time     0.209979  1.000000   0.731378  0.796144
   asc_train  0.226737  0.731378   1.000000  0.664478
   asc_car   -0.028335  0.796144   0.664478  1.000000
   

4. Elasticities

   print(elasticities(mymodel, db, 0, "TRAIN_TT"))  # CHOICE:TRAIN (0) wrt TRAIN_TT
   

   Output:

   [-0.06813523 -0.01457346 -0.0555597  ... -0.03453162 -0.02809382 -0.02343637]
   

5. Choice probability predictions

   print(mymodel.predict(db, return_choices=False))
   

   Output:

   [[0.12319342 0.54372904 0.33307754]
   [0.12267997 0.54499504 0.33232499]
   [0.12354587 0.54162143 0.3348327 ]
   ...
   [0.12801816 0.5201341  0.35184774]
   [0.1271984  0.51681635 0.35598525]
   [0.12881032 0.51856181 0.35262787]]
   

---

Development

(Optional) To develop PyCMTensor development package in a local environment, e.g. to modify, add features etc., you need to set up a virtual (Conda) environment and install the project requirements. Follow the instructions to install Conda (miniconda), then start a new virtual environment with the provided environment_<your OS>.yml file.

1. Download the git project repository into a local directory

   git clone git://github.com/mwong009/pycmtensor
   cd pycmtensor
   

Installing the virtual environment

Windows

conda env create -f environment_windows.yml

Linux

conda env create -f environment_linux.yml

Mac OSX

conda env create -f environment_macos.yml

Next, activate the virtual environment and install poetry dependency manager via pip

conda activate pycmtensor-dev
pip install poetry

Install the project and development dependencies

poetry install -E dev