8. Use examples

This page is still under development, so most of the headers are just place-holders for the actual examples


The examples provided here are not meant as a through description of AequilibraE’s capabilities. For that, please look into the API documentation or email aequilibrae@googlegroups.com

8.1. Logging

AequilibraE uses Python’s standard logging library to a file called aequilibrae.log, but the output folder for this logging can be changed to a custom system folder by altering the parameter system –> logging_directory on the parameters file.

As an example, one could do programatically change the output folder to ‘D:/myProject/logs’ by doing the following:

from aequilibrae import Parameters

fldr = 'D:/myProject/logs'

p = Parameters()
p.parameters['system']['logging_directory'] =  fldr

The other useful resource, especially during model debugging it to also show all log messages directly on the screen. Doing that requires a little knowledge of the Python Logging library, but it is just as easy:

from aequilibrae import logger
import logging

stdout_handler = logging.StreamHandler(sys.stdout)

8.2. Parameters module

Several examples on how to manipulate the parameters within AequilibraE have been shown in other parts of this tutorial.

However, in case you ever have trouble with parameter changes you have made, you can always revert them to their default values. But remember, ALL CHANGES WILL BE LOST.

from aequilibrae import Parameters

fldr = 'D:/myProject/logs'

p = Parameters()

8.3. Matrix module

  • AequilibraEMatrix

  • AequilibraEData

8.4. Project module

Let’s suppose one wants to create project files for a list of 5 cities around the world with their complete networks downloaded from Open Street Maps and place them on a local folder for analysis at a later time.

from aequilibrae.project import Project

cities = ["Darwin, Australia",
          "Karlsruhe, Germany",
          "London, UK",
          "Paris, France",
          "Auckland, New Zealand"]

for city in cities:
    pth = f'd:/net_tests/{city}.sqlite'

    p = Project(pth, True)
    del p

If one wants to load a project and check some of its properties, it is easy:

>>> from aequilibrae.project import Project

>>> p = Project('path/to_project')

# for the modes available in the model
>>> p.network.modes()
['car', 'walk', 'bicycle']

>>> p.network.count_links()

>>> p.network.count_nodes()

8.5. Paths module

from aequilibrae.paths import allOrNothing
from aequilibrae.paths import path_computation
from aequilibrae.paths.results import AssignmentResults as asgr
from aequilibrae.paths.results import PathResults as pthr

8.5.1. Path computation

8.5.2. Skimming

Let’s suppose you want to compute travel times between all zone on your network. In that case, you need only a graph that you have previously built, and the list of skims you want to compute.

from aequilibrae.paths.results import SkimResults as skmr
from aequilibrae.paths import Graph
from aequilibrae.paths import NetworkSkimming

# We instantiate the graph and load it from disk (say you created it using the QGIS GUI
g = Graph()

# You now have to set the graph for what you want
# In this case, we are computing fastest path (minimizing free flow time)

# We are also **blocking** paths from going through centroids

# We will be skimming for fftime **AND** distance along the way
g.set_skimming(['fftime', 'distance'])

# We instantiate the skim results and prepare it to have results compatible with the graph provided
result = skmr()

# We create the network skimming object and execute it
# This is multi-threaded, so if the network is too big, prepare for a slow computer
skm = NetworkSkimming(g, result)

If you want to use fewer cores for this computation (which also saves memory), you also can do it You just need to use the method set_cores before you run the skimming. Ideally it is done before preparing it

result = skmr()

And if you want to compute skims between all nodes in the network, all you need to do is to make sure the list of centroids in your graph is updated to include all nodes in the graph

from aequilibrae.paths.results import SkimResults as skmr
from aequilibrae.paths import Graph
from aequilibrae.paths import NetworkSkimming

g = Graph()

# Let's keep the original list of centroids in case we want to use it again
orig_centr = g.centroids

# Now we set the list of centroids to include all nodes in the network

# And continue **almost** like we did before
# We just need to remember to NOT block paths through centroids. Otherwise there will be no paths available
g.set_graph(cost_field='fftime', block_centroid_flows=False)

result = skmr()

skm = NetworkSkimming(g, result)

Setting skimming after setting the graph is CRITICAL, and the skim matrices are part of the result object.

You can save the results to your place of choice in AequilibraE format or export to OMX or CSV




8.5.3. Traffic assignment

A simple example of assignment

from aequilibrae.project import Project
from aequilibrae.paths import TrafficAssignment, TrafficClass
from aequilibrae.matrix import AequilibraeMatrix

assig = TrafficAssignment()

proj = Project('path/to/folder/SiouxFalls.sqlite')
# Mode c is car
car_graph = proj.network.graphs['c']

mat = AequilibraeMatrix()
# We will only assign one user class stored as 'matrix' inside the OMX file

# Creates the assignment class
assigclass = TrafficClass(g, mat)

# If you want to know which assignment algorithms are available:

# If you want to know which Volume-Delay functions are available

# The first thing to do is to add at list of traffic classes to be assigned

# Then we set the volume delay function
assig.set_vdf("BPR")  # This is not case-sensitive

# And its parameters
assig.set_vdf_parameters({"alpha": "alpha", "beta": "beta"})

# If you don't have parameters in the network, but rather global ones
# assig.set_vdf_parameters({"alpha": 0.15, "beta": 4})

# The capacity and free flow travel times as they exist in the graph

# And the algorithm we want to use to assign

# To overwrite the number of iterations and the relative gap intended
assig.max_iter = 250
assig.rgap_target = 0.0001

# To overwrite the number of CPU cores to be used

# we then execute the assignment

8.5.4. Assigning traffic on TNTP instances

There is a set of well known traffic assignment problems used in the literature maintained on GitHub that is often used for tests, so we will use one of those problems here.

Let’s suppose we want to perform traffic assignment for one of those problems and check the results against the reference results.

The parsing and importing of those networks are not really the case here, but there is online code available for doing that work.

import os
import sys
import numpy as np
import pandas as pd
from aequilibrae.paths import TrafficAssignment
from aequilibrae.paths import Graph
from aequilibrae.paths.traffic_class import TrafficClass
from aequilibrae.matrix import AequilibraeMatrix, AequilibraeData
import matplotlib.pyplot as plt

from aequilibrae import logger
import logging

# We redirect the logging output to the terminal
stdout_handler = logging.StreamHandler(sys.stdout)

# Let's work with Sioux Falls
result_file = 'SiouxFalls_flow.tntp'

# Loads and prepares the graph
g = Graph()
g.cost = np.array(g.cost, copy=True)

# Loads and prepares the matrix
mat = AequilibraeMatrix()

# Creates the assignment class
assigclass = TrafficClass(g, mat)

# Instantiates the traffic assignment problem
assig = TrafficAssignment()

# configures it properly
assig.set_vdf_parameters(**{'alpha': 0.15, 'beta': 4.0})
# could be assig.set_algorithm('frank-wolfe')

# Execute the assignment

# the results are within each traffic class only one, in this case

8.5.5. Setting multiple user classes before assignment

Let’s suppose one wants to setup a matrix for assignment that has two user classes, red_cars and blue cars for a single traffic class. To do that, one needs only to call the computational_view method with a list of the two matrices of interest. Both matrices need to be contained in the same file (and to be contiguous if an *.aem instead of a *.omx file) however.

mat = AequilibraeMatrix()
mat.computational_view(['red_cars', 'blue_cars'])

8.5.6. Advanced usage: Building a Graph

Let’s suppose now that you are interested in creating links from a bespoke procedure. For the purpose of this example, let’s say you have a sparse matrix representing a graph as an adjacency matrix

from aequilibrae.paths import Graph
from aequilibrae.project.network import Network
from scipy.sparse import coo_matrix

# original_adjacency_matrix is a sparse matrix where positive values are actual links
# where the value of the cell is the distance in that link

# We create the sparse matrix in proper sparse matrix format
sparse_graph = coo_matrix(original_adjacency_matrix)

# We create the structure to create the network
all_types = [k._Graph__integer_type,

# List of all required link fields for a network
# Network.req_link_flds

# List of all required node fields for a network
# Network.req_node_flds

# List of fields that are reserved for internal workings
# Network.protected_fields

dt = [(t, d) for t, d in zip(all_titles, all_types)]

# Number of links
num_links = sparse_graph.data.shape[0]

my_graph = Graph()
my_graph.network = np.zeros(links, dtype=dt)

my_graph.network['link_id'] = np.arange(links) + 1
my_graph.network['a_node'] = sparse_graph.row
my_graph.network['b_node'] = sparse_graph.col
my_graph.network["distance"] = sparse_graph.data

# If the links are directed (from A to B), direction is 1. If bi-directional, use zeros
my_graph.network['direction'] = np.ones(links)

# Let's say that all nodes in the network are centroids
list_of_centroids =  np.arange(max(sparse_graph.shape[0], sparse_graph.shape[0])+ 1)
centroids_list = np.array(list_of_centroids)

my_graph.type_loaded = 'NETWORK'
my_graph.status = 'OK'
my_graph.network_ok = True

This usage is really advanced, and very rarely not-necessary. Make sure to know what you are doing before going down this route

8.6. Trip distribution

The support for trip distribution in AequilibraE is not very comprehensive, mostly because of the loss of relevance that such type of model has suffered in the last decade.

However, it is possible to calibrate and apply synthetic gravity models and to perform Iterative Proportional Fitting (IPF) with really high performance, which might be of use in many applications other than traditional distribution.

8.6.1. Synthetic gravity application

In this example, imagine that you have your demographic information in an sqlite database and that you have already computed your skim matrix.

It is also important to notice that it is crucial to have consistent data, such as same set of zones (indices) in both the demographics and the impedance matrix.

import pandas as pd
import sqlite3

from aequilibrae.matrix import AequilibraeMatrix
from aequilibrae.matrix import AequilibraeData

from aequilibrae.distribution import SyntheticGravityModel
from aequilibrae.distribution import GravityApplication

# We define the model we will use
model = SyntheticGravityModel()

# Before adding a parameter to the model, you need to define the model functional form
model.function = "GAMMA" # "EXPO" or "POWER"

# Only the parameter(s) applicable to the chosen functional form will have any effect
model.alpha = 0.1
model.beta = 0.0001

# Or you can load the model from a file

# We load the impedance matrix
matrix = AequilibraeMatrix()

# We create the vectors we will use
conn = sqlite3.connect('path/to/demographics/database')
query = "SELECT zone_id, population, employment FROM demographics;"
df = pd.read_sql_query(query,conn)

index = df.zone_id.values[:]
zones = index.shape[0]

# You create the vectors you would have
df = df.assign(production=df.population * 3.0)
df = df.assign(attraction=df.employment * 4.0)

# We create the vector database
args = {"entries": zones, "field_names": ["productions", "attractions"],
    "data_types": [np.float64, np.float64], "memory_mode": True}
vectors = AequilibraeData()

# Assign the data to the vector object
vectors.productions[:] = df.production.values[:]
vectors.attractions[:] = df.attraction.values[:]
vectors.index[:] = zones[:]

# Balance the vectors
vectors.attractions[:] *= vectors.productions.sum() / vectors.attractions.sum()

args = {"impedance": matrix,
        "rows": vectors,
        "row_field": "productions",
        "model": model,
        "columns": vectors,
        "column_field": "attractions",
        "output": 'path/to/output/matrix.aem',

gravity = GravityApplication(**args)

8.6.2. Iterative Proportional Fitting (IPF)

The implementation of IPF is fully vectorized and leverages all the speed of NumPy, but it does not include the fancy multithreading implemented in path computation.

Please note that the AequilibraE matrix used as input is OVERWRITTEN by the IPF

import pandas as pd
from aequilibrae.distribution import Ipf
from aequilibrae.matrix import AequilibraeMatrix
from aequilibrae.matrix import AequilibraeData

matrix = AequilibraeMatrix()

# Here we can create from OMX or load from an AequilibraE matrix.
matrix.create_from_omx(path/to/aequilibrae_matrix, path/to/omxfile)

# The matrix will be operated one (see the note on overwriting), so it does
# not make sense load an OMX matrix

source_vectors = pd.read_csv(path/to/CSVs)
zones = source_vectors.zone.shape[0]

args = {"entries": zones, "field_names": ["productions", "attractions"],
        "data_types": [np.float64, np.float64], "memory_mode": True}

vectors = AequilibraEData()

vectors.productions[:] = source_vectors.productions[:]
vectors.attractions[:] = source_vectors.attractions[:]

# We assume that the indices would be sorted and that they would match the matrix indices
vectors.index[:] = source_vectors.zones[:]

args = {
        "matrix": matrix, "rows": vectors, "row_field": "productions", "columns": vectors,
        "column_field": "attractions", "nan_as_zero": False}

fratar = Ipf(**args)

# We can get back to our OMX matrix in the end

8.7. Matrices

Lets say we want to Import the freight matrices provided with FAF into AequilibraE’s matrix format in order to create some Delaunay Lines in QGIS or to perform traffic assignment

8.7.1. Required data

8.7.3. The code

We import all libraries we will need, including the AequilibraE

import pandas as pd
import numpy as np
import os
from aequilibrae.matrix import AequilibraeMatrix
from scipy.sparse import coo_matrix

Now we set all the paths for files and parameters we need and import the matrices into a Pandas DataFrame

data_folder = 'Y:/ALL DATA/DATA/Pedro/Professional/Data/USA/FAF/4.4'
data_file = 'FAF4.4_HiLoForecasts.csv'
sctg_names_file = 'sctg_codes.csv'  # Simplified to 50 characters, which is AequilibraE's limit
output_folder = data_folder

matrices = pd.read_csv(os.path.join(data_folder, data_file), low_memory=False)

We import the sctg codes

sctg_names = pd.read_csv(os.path.join(data_folder, sctg_names_file), low_memory=False)
sctg_names.set_index('Code', inplace=True)
sctg_descr = list(sctg_names['Commodity Description'])

We now process the matrices to collect all the data we need, such as:

  • List of zones

  • CSTG codes

  • Matrices/scenarios we are importing

all_zones = np.array(sorted(list(set( list(matrices.dms_orig.unique()) + list(matrices.dms_dest.unique())))))

# Count them and create a 0-based index
num_zones = all_zones.shape[0]
idx = np.arange(num_zones)

# Creates the indexing dataframes
origs = pd.DataFrame({"from_index": all_zones, "from":idx})
dests = pd.DataFrame({"to_index": all_zones, "to":idx})

# adds the new index columns to the pandas dataframe
matrices = matrices.merge(origs, left_on='dms_orig', right_on='from_index', how='left')
matrices = matrices.merge(dests, left_on='dms_dest', right_on='to_index', how='left')

# Lists sctg codes and all the years/scenarios we have matrices for
mat_years = [x for x in matrices.columns if 'tons' in x]
sctg_codes = matrices.sctg2.unique()

We now import one matrix for each year, saving all the SCTG codes as different matrix cores in our zoning system

# aggregate the matrix according to the relevant criteria
agg_matrix = matrices.groupby(['from', 'to', 'sctg2'])[mat_years].sum()

# returns the indices

for y in mat_years:
    mat = AequilibraeMatrix()

    # Here it does not make sense to use OMX
    # If one wants to create an OMX from other data sources, openmatrix is
    # the library to use
    kwargs = {'file_name': os.path.join(output_folder, y + '.aem'),
              'zones': num_zones,
              'matrix_names': sctg_descr}

    mat.index[:] = all_zones[:]
    # for all sctg codes
    for i in sctg_names.index:
        prod_name = sctg_names['Commodity Description'][i]
        mat_filtered_sctg = agg_matrix[agg_matrix.sctg2 == i]

        m = coo_matrix((mat_filtered_sctg[y], (mat_filtered_sctg['from'], mat_filtered_sctg['to'])),
                                           shape=(num_zones, num_zones)).toarray().astype(np.float64)

        mat.matrix[prod_name][:,:] = m[:,:]