od and od_probs in DiscretionaryTrips

[Hussein-Mahfouz]

I really like this package and I'm hoping to use it for building an activity-based model. I'm trying to understand how to assign locations for discretionary trips, and I have a couple of questions I'm hoping you can help me with:

1. od_probs (origin-destination probabilities)

• how do you calculate the probabilities in od_probs? Would they be based on a spatial interaction model?
• Should the probabilities be different for different activity types? I think probability is a function of (a) distance and (b) the number of facilities that match the activity type in the zone. (b) will differ per activity

2. od

od is a multi-dimensional array of the origin-destination data (link to your code). In your example you define both a distance and a time matrix, do I need both? I think in your function only time is used, but maybe I'm missing something