DITRAS (DIary-based TRAjectory Simulator), a mathematical model to simulate human mobility
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README.md

DITRAS

DITRAS (DIary-based TRAjectory Simulator) is a framework to simulate the spatio-temporal patterns of human mobility in a realistic way. DITRAS operates in two steps: the generation of a mobility diary and the translation of the mobility diary into a mobility trajectory. The mobility diary is constructed by a Markov model which captures the tendency of individuals to follow or break their routine. The mobility trajectory is produced by a model based on the concept of preferential exploration and preferential return. DITRAS can reproduce the statistical properties of real human mobility trajectories in an accurate way. For technical details on DITRAS please read the scientific article at this link: http://arxiv.org/abs/1607.05952

Citation

If you use this code, please cite the following scientific article:

Required Python packages

  • random
  • cPickle
  • math
  • scipy
  • collections
  • numpy
  • sys
  • os
  • time
  • csv

How to run DITRAS as standalone

To run the code of DITRAS, download all the folder in this repository and write on the terminal a command in the following format:
python DITRAS.py n_agents time_slots spatial_tessellation od_matrix diary_generator_1hour.pkl filename, where:

  • n_agents is an integer indicating the number of agents to simulate (e.g., 10000)
  • time_slots is the length of the time period in hours (e.g., 720, that is 1 month)
  • spatial_tessellation is the name of a file where the weighted spatial tessellation is stored. The format of the spatial_tessellation file must be the following: latitude,longitude,relevance. Latitude and longitude are float numbers indicating the geographic position of a location and relevance is an integer indicating the importance of the location (e.g., the number of residents in the locations or the number of calls made in that location during a given period). We provide you an example of spatial tessellation in the Italian regione of Trentino, stored in the file location2info_trentino. This spatial tessellation is released under a Open Data Commons Open Database License (ODbL) and it is obtained from the publicly available dataset described in this paper http://www.nature.com/articles/sdata201555#data-records.
  • od_matrix is the name of a file where the origin-destination matrix based on the spatial_tessellation is stored. The origin-destination matrix is used by DITRAS to decide the movements of the synthetic agents. If the file specified does not exist in the current folder, DITRAS will automatically compute the origin-destination matrix and store it in a file named od_matrix.
  • diary_generator_1hour.pkl is the diary generator we computed for you, stored as a pickle file. If you have real trajectory data, you can compute your own diary generator using the Python script diary_generator_builder.py.

For example type the following command on the terminal to start your DITRAS simulation:

python DITRAS.py 10000 720 location2info_trentino od_matrix.pkl diary_generator_1hour.pkl trajs_10000_720.csv 

DITRAS will simulate the mobility of 10,000 agents for 720 hours (1 months), using the location2info_trentino weighted spatial tessellation and the diary generator diary_generator_1hour.pkl. The produced synthetic trajectories will be stored in a file named trajs_10000_720.csv. DITRAS will also compute the origin destination matrix od_matrix.pkl the first time you run the command.

How to run DITRAS as library

First, read the spatial tessellation from the corresponding file and load it in a dictionary, using the function load_spatial_tessellation. In this repository we provide an example of spatial tessellation regarding the Italian region of Trentino, it is stored in the file location2info_trentino. Second, initialize a DITRAS object with the parameters you prefer. Finally, start the execution of DITRAS by using the method start_simulation.

spatial_tessellation = load_spatial_tessellation('location2info_trentino')

ditras = DITRAS(n_agents=10000, length=720, diary_generator=MD(filename='diary_generator_1hour.pkl'),
                 trajectory_generator=dEPR(rho=0.6, gamma=0.21), filename='trajs_10000_720.csv')

ditras.start_simulation(spatial_tessellation, od_matrix_file='od_matrix.pkl')

Run the ditras_example.ipynb notebook in this repository to try different executions of DITRAS.

Output of DITRAS

DITRAS produces a file with the following format:

agent_id,location_id,time_slot

where:

  • agent_id is an identifier of the agent
  • location_id is the identifier of the location visited by the agent, as specified in the spatial tessellation file
  • time_slot is the time slot of the visit, i.e., the hour when the agent visited the location