Final Project Repository Template

This is the final project repository for Colby Wise and Michael Alvarino's Machine Learning with Probabilistic Programming final Project

Problem Formulation

Can we use probabilistic programming to create a generative model of trip durations for taxi trips in New York City?

Dataset

We will be using the NYC Yellow Cab Dataset, specifically the data for 2016. This included approximately 1.8 million trips between January and June. We initially preprocessed the data ourselves to add neighborhoods of the pickups and dropoffs, but later found a copy of the dataset that already included the preprocessing. The preprocessing we performed initially is included in our preprocessing directory.

Box's Loop 1

Our first iteration through Box's loop was as simple as we could try, a Baysian Gaussian Linear Model such that $y = f(X) + b$ where $f(X) = WX$. We placed a gaussian prior on both $W$ and $b$. The model was surprisingly accurate, but we thought it could be improved by finidng some interaction between our features with a basis function.

Box's Loop 2

Our second iteration through Box's loop added a basis function to our gaussian linear model. We decided to try a simple polynomial basis, so that $basis(X_i, degree) = [X_i, X_i ^ 2, X_i^3, ..., X_i^degree]$, to the polynomial degree specified. We found that this model improved accuracy, but as shown by our PPC did not model our original data well.

Box's Loop 3

Understanding that there were infinitely many basis functions and that we could not check and test them all, we decided to use a gaussian process. We tested two different kernels, the gaussian kernel, and the rational quadratic. We found that the gaussian process, though not a more accurate prdictor of trip duration, was a much better model of our generative process.

Next Steps

Use tensorflow to optimize the parameters of the gaussian process kernel function