def compute_adjacency_list(input_points, input_network, id_attribute,
impedance_attribute, accumulator_attributes,
search_radius, output_location, adj_dbf_name):
"""
|input_points|: point shape file marking entity (e.g. building) locations
|input_network|: street network in which |input_points| is located
|id_attribute|: the name of attribute that distinguishes between input points
|impedance_attribute|: distance between neighboring nodes will be based on
this attribute
|accumulator_attributes|: distance between neighboring nodes will also be
recorded for these attributes
|search_radius|: the maximum extent for centrality computation
|output_location|: adjacency list dbf will be saved here
|adj_dbf_name|: the name of the adjacency list dbf
"""
# Number of points in |input_points|
input_point_count = int(GetCount_management(input_points).getOutput(0))
# Make a directory to store all auxiliary files
auxiliary_dir = join(output_location, AUXILIARY_DIR_NAME)
if not Exists(auxiliary_dir):
mkdir(auxiliary_dir)
# Record the edge and junction source names of |input_network|
junction_feature, edge_feature = network_features(input_network)
# Calculate network locations if not already calculated
test_input_point = UpdateCursor(input_points).next()
locations_calculated = all(
row_has_field(test_input_point, field)
for field in NETWORK_LOCATION_FIELDS)
if not locations_calculated:
calculate_network_locations(input_points, input_network)
# Calculate barrier cost per input point if not already calculated
barrier_costs_calculated = row_has_field(test_input_point,
trim(BARRIER_COST_FIELD))
if not barrier_costs_calculated:
AddMessage(BARRIER_COST_COMPUTATION_STARTED)
# Add |BARRIER_COST_FIELD| column in |input_points|
AddField_management(in_table=input_points,
field_name=trim(BARRIER_COST_FIELD),
field_type="DOUBLE",
field_is_nullable="NON_NULLABLE")
# Initialize a dictionary to store the frequencies of (SnapX, SnapY) values
xy_count = {}
# A method to retrieve a (SnapX, SnapY) pair for a row in |input_points|
get_xy = lambda row: (row.getValue(trim("SnapX")),
row.getValue(trim("SnapY")))
barrier_pre_progress = Progress_Bar(input_point_count, 1,
BARRIER_COST_PRE_PROCESSING)
rows = UpdateCursor(input_points)
for row in rows:
snap_xy = get_xy(row)
if snap_xy in xy_count:
xy_count[snap_xy] += 1
else:
xy_count[snap_xy] = 1
barrier_pre_progress.step()
# Populate |BARRIER_COST_FIELD|, this will be used in OD matrix computation
barrier_progress = Progress_Bar(input_point_count, 1,
BARRIER_COST_COMPUTATION)
rows = UpdateCursor(input_points)
for row in rows:
barrier_cost = BARRIER_COST / xy_count[get_xy(row)]
row.setValue(trim(BARRIER_COST_FIELD), barrier_cost)
rows.updateRow(row)
barrier_progress.step()
AddMessage(BARRIER_COST_COMPUTATION_FINISHED)
# Necessary files
od_cost_matrix_layer = join(auxiliary_dir, OD_COST_MATRIX_LAYER_NAME)
od_cost_matrix_lines = join(od_cost_matrix_layer, OD_COST_MATRIX_LINES)
temp_adj_dbf_name = TEMP_ADJACENCY_DBF_NAME(adj_dbf_name)
temp_adj_dbf = join(output_location, temp_adj_dbf_name)
adj_dbf = join(output_location, adj_dbf_name)
partial_adj_dbf = join(auxiliary_dir, PARTIAL_ADJACENCY_LIST_NAME)
polygons = join(auxiliary_dir, POLYGONS_SHAPEFILE_NAME)
raster = join(auxiliary_dir, RASTER_NAME)
polygons_layer = join(auxiliary_dir, POLYGONS_LAYER_NAME)
input_points_layer = join(auxiliary_dir, INPUT_POINTS_LAYER_NAME)
# Make sure none of these files already exists
for path in [
od_cost_matrix_layer, temp_adj_dbf, adj_dbf, partial_adj_dbf,
polygons, raster, polygons_layer, input_points_layer,
od_cost_matrix_lines
]:
delete(path)
# Cutoff radius for OD matrix computation
cutoff_radius = 2 * BARRIER_COST + min(search_radius, BARRIER_COST / 2)
# Compute OD matrix
MakeODCostMatrixLayer_na(in_network_dataset=input_network,
out_network_analysis_layer=od_cost_matrix_layer,
impedance_attribute=impedance_attribute,
default_cutoff=str(cutoff_radius),
accumulate_attribute_name=accumulator_attributes,
UTurn_policy="ALLOW_UTURNS",
hierarchy="NO_HIERARCHY",
output_path_shape="NO_LINES")
# Determine raster cell size
points_per_raster_cell = OD_MATRIX_ENTRIES / input_point_count
raster_cell_count = max(1, input_point_count / points_per_raster_cell)
input_points_extent = Describe(input_points).Extent
raster_cell_area = (input_points_extent.width *
input_points_extent.height / raster_cell_count)
raster_cell_size = int(sqrt(raster_cell_area))
# Construct |raster| from |input_points|
PointToRaster_conversion(in_features=input_points,
value_field=id_attribute,
out_rasterdataset=raster,
cell_assignment="MOST_FREQUENT",
priority_field="NONE",
cellsize=str(raster_cell_size))
# Construct |polygons| from |raster|
RasterToPolygon_conversion(in_raster=raster,
out_polygon_features=polygons,
simplify="NO_SIMPLIFY",
raster_field="VALUE")
# Export empty |od_cost_matrix_lines| to |temp_dbf| to start adjacency list
TableToTable_conversion(in_rows=od_cost_matrix_lines,
out_path=output_location,
out_name=temp_adj_dbf_name)
# Construct |polygons_layer| and |input_points_layer|
for (feature, layer) in [(polygons, polygons_layer),
(input_points, input_points_layer)]:
MakeFeatureLayer_management(in_features=feature, out_layer=layer)
def add_locations(sub_layer, field_mappings=""):
"""
|sub_layer|: one of "Origins", "Destinations", "Barrier Points"
|field_mappings|: field mappings in addition to those for "Name" and
"CurbApproach"
"""
AddLocations_na(in_network_analysis_layer=od_cost_matrix_layer,
sub_layer=sub_layer,
in_table=input_points_layer,
field_mappings=("Name %s #; CurbApproach # 0; %s" %
(id_attribute, field_mappings)),
search_tolerance=SEARCH_TOLERANCE,
search_criteria=("%s SHAPE; %s SHAPE;" %
(junction_feature, edge_feature)),
append="CLEAR",
snap_to_position_along_network="SNAP",
snap_offset=SNAP_OFFSET)
# OD cost matrix destinations
AddMessage(ADDING_DESTINATIONS_STARTED)
SelectLayerByLocation_management(in_layer=input_points_layer)
add_locations("Destinations")
AddMessage(ADDING_DESTINATIONS_FINISHED)
# OD cost matrix point barriers
AddMessage(ADDING_BARRIERS_STARTED)
add_locations("Point Barriers",
("FullEdge # 0; BarrierType # 2;"
"Attr_%s %s #;" %
(impedance_attribute, trim(BARRIER_COST_FIELD))))
AddMessage(ADDING_BARRIERS_FINISHED)
# Compute adjacency list, one raster cell at a time
progress = Progress_Bar(raster_cell_count, 1, STEP_1)
rows = UpdateCursor(polygons)
for row in rows:
# Select the current polygon
SelectLayerByAttribute_management(in_layer_or_view=polygons_layer,
selection_type="NEW_SELECTION",
where_clause="FID = %s" %
str(row.FID))
# Origins
SelectLayerByLocation_management(in_layer=input_points_layer,
select_features=polygons_layer)
add_locations("Origins")
# Solve OD Cost matrix
Solve_na(in_network_analysis_layer=od_cost_matrix_layer,
ignore_invalids="SKIP")
# Add origin and destination fields to the adjacency list dbf
for (index, field) in [(0, ORIGIN_ID_FIELD_NAME),
(1, DESTINATION_ID_FIELD_NAME)]:
CalculateField_management(in_table=od_cost_matrix_lines,
field=field,
expression="!Name!.split(' - ')[%d]" %
index,
expression_type="PYTHON")
# Record actual distance between neighboring nodes
distance_field = "Total_%s" % impedance_attribute
CalculateField_management(in_table=od_cost_matrix_lines,
field=distance_field,
expression="!%s! - 2 * %d" %
(distance_field, BARRIER_COST),
expression_type="PYTHON")
# Append result to |temp_adj_dbf|
TableToTable_conversion(in_rows=od_cost_matrix_lines,
out_path=auxiliary_dir,
out_name=PARTIAL_ADJACENCY_LIST_NAME)
Append_management(inputs=partial_adj_dbf,
target=temp_adj_dbf,
schema_type="TEST")
progress.step()
# Copy data from |temp_adj_dbf| to |adj_dbf|
Rename_management(in_data=temp_adj_dbf, out_data=adj_dbf)
# Clean up
for path in [
od_cost_matrix_layer, partial_adj_dbf, polygons, raster,
polygons_layer, input_points_layer, auxiliary_dir
]:
delete(path)
def compute_centrality(nodes, origins, compute_r, compute_g, compute_b,
compute_c, compute_s, radius, network_radius, beta, measures_to_normalize,
accumulator_fields):
"""
Computes reach, gravity, betweenness, closeness, and straightness on a graph.
|nodes|: graph representation; dictionary mapping node id's to |Node| objects
|origins|: subset of nodes that will be used as sources of shortest path trees
|compute_r|: compute reach?
|compute_g|: compute gravity type index?
|compute_b|: compute betweenness?
|compute_c|: compute closeness?
|compute_s|: compute straightness?
|radius|: for each node, only consider other nodes that can be reached within
this distance
|network_radius|: use network radius or birds-eye radius?
|beta|: parameter for gravity type index
|measures_to_normalize|: a list of measures to normalize
|accumulator_fields|: a list of cost attributes to accumulate
"""
# Number of nodes in the graph
N = len(nodes)
O = len(origins)
if O > N:
raise Invalid_Parameters_Exception("size of origins exceeds size of nodes")
elif O == 0:
return
# Preprocessing
have_accumulations = len(accumulator_fields) > 0
if have_accumulations:
empty_accumulations = lambda: dict((field, 0.0) for field in
accumulator_fields)
have_locations = hasattr(nodes.values()[0], LOCATION)
if compute_s and not have_locations:
# We cannot compute straightness without node locations
compute_s = False
if compute_b:
# Initialize betweenness values
for id in nodes:
setattr(nodes[id], BETWEENNESS, 0.0)
# Initialize the sum of all node weights (normalization)
sum_weights = 0.0
# Computation
progress = Progress_Bar(O, 1, STEP_4)
for s in origins:
if s not in nodes:
continue
weight_s = getattr(nodes[s], WEIGHT)
if have_locations: location_s = getattr(nodes[s], LOCATION)
sum_weights += weight_s
# Initialize reach (weighted and unweighted) computation for |s|
# (normalization)
reach_s = -1
weighted_reach_s = -weight_s
# Initialize measures
if compute_g: gravity_s = 0.0
if compute_b:
P = {s: []} # Predecessors
S = [] # Stack containing nodes in the order they are extended
sigma = {s: 1.0} # Number of shortest paths from |s| to other nodes
delta = {} # Dependency of |s| on other nodes
if compute_c: d_sum_s = 0.0
if compute_s: straightness_s = 0.0
if have_accumulations:
accumulations_s = {s: empty_accumulations()}
d = {s: 0.0} # Shortest distance from |s| to other nodes
# Queue for Dijkstra
Q = [(0.0, s)] if network_radius else [(0.0, s, 0.0)]
# If we use euclidean radius, make a list of all reachable nodes
if not network_radius:
reachable_s = set()
for t in nodes:
location_t = getattr(nodes[t], LOCATION)
if dist(location_s, location_t) <= radius:
reachable_s.add(t)
# Dijkstra
while Q and (True if network_radius else reachable_s):
# Pop the closest node to |s| from |Q|
if network_radius:
d_sv, v = heappop(Q)
else:
d_sv, v, dist_sv = heappop(Q)
if v in reachable_s:
reachable_s.remove(v)
weight_v = getattr(nodes[v], WEIGHT)
if have_locations: location_v = getattr(nodes[v], LOCATION)
compute = network_radius or dist_sv <= radius
if compute:
reach_s += 1
weighted_reach_s += weight_v
if d_sv > 0:
if compute_g: gravity_s += weight_v * exp(-d_sv * beta)
if compute_c: d_sum_s += weight_v * d_sv
if compute_s: straightness_s += (weight_v *
dist(location_s, location_v) / d_sv)
if compute_b: S.append(v)
for w, d_vw, accumulations_vw in getattr(nodes[v], NEIGHBORS):
# s ~ ... ~ v ~ w
d_sw = d_sv + d_vw
if not network_radius:
# Use Euclidean distance
location_w = getattr(nodes[w], LOCATION)
dist_sw = dist(location_s, location_w)
if compute_b: b_refresh = False
add_w_to_Q = False
if not w in d: # Found a path from |s| to |w| for the first time
if d_sw <= radius or not network_radius:
add_w_to_Q = True
d[w] = d_sw
if compute_b: b_refresh = True
elif lt_tol(d_sw, d[w]): # Found a better path from |s| to |w|
if d_sw <= radius or not network_radius:
if d[w] <= radius or not network_radius:
longer_path_node = (d[w], w) if network_radius else (d[w], w,
dist_sw)
Q.remove(longer_path_node)
heapify(Q)
add_w_to_Q = True
d[w] = d_sw
if compute_b: b_refresh = True
if add_w_to_Q:
new_node = (d_sw, w) if network_radius else (d_sw, w, dist_sw)
heappush(Q, new_node)
if have_accumulations:
accumulations_s[w] = merge_maps(accumulations_s[v],
dict(accumulations_vw), add)
if compute_b:
if b_refresh:
sigma[w] = 0.0
P[w] = []
if eq_tol(d_sw, d[w]): # Count all shortest paths from |s| to |w|
sigma[w] += sigma[v] # Update the number of shortest paths
P[w].append(v) # |v| is a predecessor of |w|
delta[v] = 0.0 # Recognize |v| as a predecessor
if compute_r: setattr(nodes[s], REACH, weighted_reach_s)
if compute_g: setattr(nodes[s], GRAVITY, gravity_s)
if compute_b:
while S: # Revisit nodes in reverse order of distance from |s|
w = S.pop()
delta_w = delta[w] if w in delta else 0.0 # Dependency of |s| on |w|
for v in P[w]:
weight_w = getattr(nodes[w], WEIGHT)
delta[v] += sigma[v] / sigma[w] * (weight_w + delta_w)
if w != s:
between_w = getattr(nodes[w], BETWEENNESS)
setattr(nodes[w], BETWEENNESS, between_w + delta_w)
if compute_c: setattr(nodes[s], CLOSENESS, (1.0 / d_sum_s if d_sum_s > 0
else 0.0))
if compute_s: setattr(nodes[s], STRAIGHTNESS, straightness_s)
nodes[s].reach = reach_s
nodes[s].weighted_reach = weighted_reach_s
if have_accumulations:
total_accumulations_s = empty_accumulations()
for v in accumulations_s:
total_accumulations_s = merge_maps(total_accumulations_s,
accumulations_s[v], add)
for field in accumulator_fields:
setattr(nodes[s], field, total_accumulations_s[field])
progress.step()
# Normalization
if BETWEENNESS in measures_to_normalize and O < N:
measures_to_normalize.remove(BETWEENNESS)
AddWarning(WARNING_NO_BETWEENNESS_NORMALIZATION)
if measures_to_normalize:
norm_progress = Progress_Bar(O, 1, PROGRESS_NORMALIZATION)
for s in origins:
if s not in nodes:
continue
reach_s = nodes[s].reach
weighted_reach_s = nodes[s].weighted_reach
# Normalize reach
if compute_r and REACH in measures_to_normalize:
weight_s = getattr(nodes[s], WEIGHT)
try: setattr(nodes[s], NORM_REACH, reach_s / (sum_weights - weight_s))
except: setattr(nodes[s], NORM_REACH, 0.0)
# Normalize gravity
if compute_g and GRAVITY in measures_to_normalize:
gravity_s = getattr(nodes[s], GRAVITY)
try: setattr(nodes[s], NORM_GRAVITY, (exp(beta) * gravity_s /
weighted_reach_s))
except: setattr(nodes[s], NORM_GRAVITY, 0.0)
# Normalize betweenness
if compute_b and BETWEENNESS in measures_to_normalize:
betweenness_s = getattr(nodes[s], BETWEENNESS)
try: setattr(nodes[s], NORM_BETWEENNESS, (betweenness_s /
(weighted_reach_s * (reach_s - 1))))
except: setattr(nodes[s], NORM_BETWEENNESS, 0.0)
# Normalize closeness
if compute_c and CLOSENESS in measures_to_normalize:
closeness_s = getattr(nodes[s], CLOSENESS)
try: setattr(nodes[s], NORM_CLOSENESS, closeness_s * weighted_reach_s)
except: setattr(nodes[s], NORM_CLOSENESS, 0.0)
# Normalize straightness
if compute_s and STRAIGHTNESS in measures_to_normalize:
straightness_s = getattr(nodes[s], STRAIGHTNESS)
try: setattr(nodes[s], NORM_STRAIGHTNESS, (straightness_s /
weighted_reach_s))
except: setattr(nodes[s], NORM_STRAIGHTNESS, 0.0)
norm_progress.step()
def compute_centrality(nodes, origins, compute_r, compute_g, compute_b,
compute_c, compute_s, radius, beta, measures_to_normalize,
accumulator_fields):
"""
Computes reach, gravity, betweenness, closeness, and straightness on a graph.
|nodes|: graph representation; dictionary mapping node id's to |Node| objects
|origins|: subset of nodes that will be used as sources of shortest path trees
|compute_r|: compute reach?
|compute_g|: compute gravity type index?
|compute_b|: compute betweenness?
|compute_c|: compute closeness?
|compute_s|: compute straightness?
|radius|: for each node, only consider other nodes that can be reached within
this distance
|beta|: parameter for gravity type index
|measures_to_normalize|: a list of measures to normalize
|accumulator_fields|: a list of cost attributes to accumulate
"""
# Number of nodes in the graph
N = len(nodes)
O = len(origins)
if N == 0 or O == 0:
return
# Preprocessing
have_accumulations = len(accumulator_fields) > 0
have_locations = hasattr(nodes.values()[0], LOCATION)
if compute_s and not have_locations:
# We cannot compute straightness without node locations
compute_s = False
if compute_b:
# Initialize betweenness values
for id in nodes:
setattr(nodes[id], BETWEENNESS, 0.0)
# Initialize the sum of all node weights (normalization)
sum_weights = 0.0
# Computation
progress = Progress_Bar(O, 1, STEP_4)
for s in origins:
weight_s = getattr(nodes[s], WEIGHT)
if have_locations: location_s = getattr(nodes[s], LOCATION)
sum_weights += weight_s
# Initialize reach (weighted and unweighted) computation for |s|
# (normalization)
reach_s = -1
weighted_reach_s = -weight_s
# Initialize measures
if compute_g: gravity_s = 0.0
if compute_b:
P = {s: []} # Predecessors
S = [] # Stack containing nodes in the order they are extended
sigma = {s: 1.0} # Number of shortest paths from |s| to other nodes
delta = {} # Dependency of |s| on other nodes
if compute_c: d_sum_s = 0.0
if compute_s: straightness_s = 0.0
if have_accumulations:
empty_accumulations = lambda: dict((field, 0.0) for field in
accumulator_fields)
accumulations_s = {s: empty_accumulations()}
d = {s: 0.0} # Shortest distance from |s| to other nodes
Q = [(0.0, s)] # Queue for Dijkstra
# Dijkstra
while Q:
# Pop the closest node to |s| from |Q|
d_sv, v = heappop(Q)
weight_v = getattr(nodes[v], WEIGHT)
if have_locations: location_v = getattr(nodes[v], LOCATION)
reach_s += 1
weighted_reach_s += weight_v
if d_sv > 0:
if compute_g: gravity_s += weight_v * exp(-d_sv * beta)
if compute_c: d_sum_s += weight_v * d_sv
if compute_s: straightness_s += (weight_v * dist(location_s, location_v)
/ d_sv)
if compute_b: S.append(v)
for w, d_vw, accumulations_vw in getattr(nodes[v], NEIGHBORS):
# s ~ ... ~ v ~ w
d_sw = d_sv + d_vw
if compute_b: b_refresh = False
if not w in d: # Found a path from |s| to |w| for the first time
if d_sw <= radius:
heappush(Q, (d_sw, w)) # Add |w| to |Q|
if have_accumulations:
accumulations_s[w] = merge_maps(accumulations_s[v],
dict(accumulations_vw), add)
d[w] = d_sw
if compute_b: b_refresh = True
elif lt_tol(d_sw, d[w]): # Found a better path from |s| to |w|
if d_sw <= radius:
if d[w] <= radius:
Q.remove((d[w], w))
heapify(Q)
heappush(Q, (d_sw, w)) # Add |w| to |Q|
if have_accumulations:
accumulations_s[w] = merge_maps(accumulations_s[v],
dict(accumulations_vw), add)
d[w] = d_sw
if compute_b: b_refresh = True
if compute_b:
if b_refresh:
sigma[w] = 0.0
P[w] = []
if eq_tol(d_sw, d[w]): # Count all shortest paths from |s| to |w|
sigma[w] += sigma[v] # Update the number of shortest paths
P[w].append(v) # |v| is a predecessor of |w|
delta[v] = 0.0 # Recognize |v| as a predecessor
if compute_r: setattr(nodes[s], REACH, weighted_reach_s)
if compute_g: setattr(nodes[s], GRAVITY, gravity_s)
if compute_b:
while S: # Revisit nodes in reverse order of distance from |s|
w = S.pop()
delta_w = delta[w] if w in delta else 0.0 # Dependency of |s| on |w|
for v in P[w]:
weight_w = getattr(nodes[w], WEIGHT)
delta[v] += sigma[v] / sigma[w] * (weight_w + delta_w)
if w != s:
between_w = getattr(nodes[w], BETWEENNESS)
setattr(nodes[w], BETWEENNESS, between_w + delta_w)
if compute_c: setattr(nodes[s], CLOSENESS, (1.0 / d_sum_s if d_sum_s > 0
else 0.0))
if compute_s: setattr(nodes[s], STRAIGHTNESS, straightness_s)
nodes[s].reach = reach_s
nodes[s].weighted_reach = weighted_reach_s
if have_accumulations:
total_accumulations_s = empty_accumulations()
for v in accumulations_s:
total_accumulations_s = merge_maps(total_accumulations_s,
accumulations_s[v], add)
for field in accumulator_fields:
setattr(nodes[s], field, total_accumulations_s[field])
progress.step()
# Normalization
if BETWEENNESS in measures_to_normalize and O < N:
measures_to_normalize.remove(BETWEENNESS)
AddWarning(WARNING_NO_BETWEENNESS_NORMALIZATION)
if measures_to_normalize:
norm_progress = Progress_Bar(O, 1, PROGRESS_NORMALIZATION)
for s in origins:
reach_s = nodes[s].reach
weighted_reach_s = nodes[s].weighted_reach
# Normalize reach
if compute_r and REACH in measures_to_normalize:
weight_s = getattr(nodes[s], WEIGHT)
try: setattr(nodes[s], NORM_REACH, reach_s / (sum_weights - weight_s))
except: setattr(nodes[s], NORM_REACH, 0.0)
# Normalize gravity
if compute_g and GRAVITY in measures_to_normalize:
gravity_s = getattr(nodes[s], GRAVITY)
try: setattr(nodes[s], NORM_GRAVITY, (exp(beta) * gravity_s /
weighted_reach_s))
except: setattr(nodes[s], NORM_GRAVITY, 0.0)
# Normalize betweenness
if compute_b and BETWEENNESS in measures_to_normalize:
betweenness_s = getattr(nodes[s], BETWEENNESS)
try: setattr(nodes[s], NORM_BETWEENNESS, (betweenness_s /
(weighted_reach_s * (reach_s - 1))))
except: setattr(nodes[s], NORM_BETWEENNESS, 0.0)
# Normalize closeness
if compute_c and CLOSENESS in measures_to_normalize:
closeness_s = getattr(nodes[s], CLOSENESS)
try: setattr(nodes[s], NORM_CLOSENESS, closeness_s * weighted_reach_s)
except: setattr(nodes[s], NORM_CLOSENESS, 0.0)
# Normalize straightness
if compute_s and STRAIGHTNESS in measures_to_normalize:
straightness_s = getattr(nodes[s], STRAIGHTNESS)
try: setattr(nodes[s], NORM_STRAIGHTNESS, (straightness_s /
weighted_reach_s))
except: setattr(nodes[s], NORM_STRAIGHTNESS, 0.0)
norm_progress.step()
AddMessage(STEP_1_FAILED)
success = False
# Step 2
if success:
AddMessage(STEP_2_STARTED)
try:
distance_field = trim("Total_%s" % inputs[IMPEDANCE_ATTRIBUTE])
accumulator_fields = set([trim("Total_%s" % accumulator_attribute)
for accumulator_attribute in inputs[ACCUMULATOR_ATTRIBUTES].split(";")
if accumulator_attribute != "#"])
# Graph representation: dictionary mapping node id's to Node objects
nodes = {}
# The number of rows in |adj_dbf|
directed_edge_count = int(GetCount_management(adj_dbf).getOutput(0))
graph_progress = Progress_Bar(directed_edge_count, 1, STEP_2)
rows = UpdateCursor(adj_dbf)
for row in rows:
# Get neighboring nodes, and the distance between them
origin_id = row.getValue(trim(ORIGIN_ID_FIELD_NAME))
destination_id = row.getValue(trim(DESTINATION_ID_FIELD_NAME))
distance = float(row.getValue(distance_field))
# Make sure the nodes are recorded in the graph
for id in [origin_id, destination_id]:
if not id in nodes:
nodes[id] = Node()
# Make sure that the nodes are neighbors in the graph
if origin_id != destination_id and distance >= 0:
accumulations = {}
for field in accumulator_fields:
accumulations[field] = float(row.getValue(field))
def compute_adjacency_list(input_points, input_network, id_attribute,
impedance_attribute, accumulator_attributes, search_radius, output_location,
adj_dbf_name):
"""
|input_points|: point shape file marking entity (e.g. building) locations
|input_network|: street network in which |input_points| is located
|id_attribute|: the name of attribute that distinguishes between input points
|impedance_attribute|: distance between neighboring nodes will be based on
this attribute
|accumulator_attributes|: distance between neighboring nodes will also be
recorded for these attributes
|search_radius|: the maximum extent for centrality computation
|output_location|: adjacency list dbf will be saved here
|adj_dbf_name|: the name of the adjacency list dbf
"""
# Number of points in |input_points|
input_point_count = int(GetCount_management(input_points).getOutput(0))
# Make a directory to store all auxiliary files
auxiliary_dir = join(output_location, AUXILIARY_DIR_NAME)
if not Exists(auxiliary_dir):
mkdir(auxiliary_dir)
# Record the edge and junction source names of |input_network|
edge_feature = None
junction_feature = None
for source in Describe(input_network).sources:
if source.sourceType == EDGE_FEATURE:
edge_feature = source.name
elif source.sourceType in JUNCTION_FEATURE:
junction_feature = source.name
if edge_feature == None:
AddWarning(WARNING_NO_EDGE_FEATURE(input_network))
raise Invalid_Input_Exception("Input Network")
if junction_feature == None:
AddWarning(WARNING_NO_JUNCTION_FEATURE(input_network))
raise Invalid_Input_Exception("Input Network")
# Calculate network locations if not already calculated
test_input_point = UpdateCursor(input_points).next()
locations_calculated = all(row_has_field(test_input_point, field)
for field in NETWORK_LOCATION_FIELDS)
if not locations_calculated:
AddMessage(CALCULATE_LOCATIONS_STARTED)
CalculateLocations_na(in_point_features=input_points,
in_network_dataset=input_network,
search_tolerance=SEARCH_TOLERANCE,
search_criteria=("%s SHAPE; %s SHAPE;" %
(junction_feature, edge_feature)),
exclude_restricted_elements="INCLUDE")
AddMessage(CALCULATE_LOCATIONS_FINISHED)
# Calculate barrier cost per input point if not already calculated
barrier_costs_calculated = row_has_field(test_input_point,
trim(BARRIER_COST_FIELD))
if not barrier_costs_calculated:
AddMessage(BARRIER_COST_COMPUTATION_STARTED)
# Add |BARRIER_COST_FIELD| column in |input_points|
AddField_management(in_table=input_points,
field_name=trim(BARRIER_COST_FIELD), field_type="DOUBLE",
field_is_nullable="NON_NULLABLE")
# Initialize a dictionary to store the frequencies of (SnapX, SnapY) values
xy_count = {}
# A method to retrieve a (SnapX, SnapY) pair for a row in |input_points|
get_xy = lambda row: (row.getValue(trim("SnapX")),
row.getValue(trim("SnapY")))
barrier_pre_progress = Progress_Bar(input_point_count, 1,
BARRIER_COST_PRE_PROCESSING)
rows = UpdateCursor(input_points)
for row in rows:
snap_xy = get_xy(row)
if snap_xy in xy_count:
xy_count[snap_xy] += 1
else:
xy_count[snap_xy] = 1
barrier_pre_progress.step()
# Populate |BARRIER_COST_FIELD|, this will be used in OD matrix computation
barrier_progress = Progress_Bar(input_point_count, 1,
BARRIER_COST_COMPUTATION)
rows = UpdateCursor(input_points)
for row in rows:
barrier_cost = BARRIER_COST / xy_count[get_xy(row)]
row.setValue(trim(BARRIER_COST_FIELD), barrier_cost)
rows.updateRow(row)
barrier_progress.step()
AddMessage(BARRIER_COST_COMPUTATION_FINISHED)
# Necessary files
od_cost_matrix_layer = join(auxiliary_dir, OD_COST_MATRIX_LAYER_NAME)
od_cost_matrix_lines = join(od_cost_matrix_layer, OD_COST_MATRIX_LINES)
temp_adj_dbf_name = "%s~.dbf" % adj_dbf_name[:-4]
temp_adj_dbf = join(output_location, temp_adj_dbf_name)
adj_dbf = join(output_location, adj_dbf_name)
partial_adj_dbf = join(auxiliary_dir, PARTIAL_ADJACENCY_LIST_NAME)
polygons = join(auxiliary_dir, POLYGONS_SHAPEFILE_NAME)
raster = join(auxiliary_dir, RASTER_NAME)
polygons_layer = join(auxiliary_dir, POLYGONS_LAYER_NAME)
input_points_layer = join(auxiliary_dir, INPUT_POINTS_LAYER_NAME)
# Make sure none of these files already exists
for path in [od_cost_matrix_layer, temp_adj_dbf, adj_dbf, partial_adj_dbf,
polygons, raster, polygons_layer, input_points_layer,
od_cost_matrix_lines]:
delete(path)
# Cutoff radius for OD matrix computation
cutoff_radius = 2 * BARRIER_COST + min(search_radius, BARRIER_COST / 2)
# Compute OD matrix
MakeODCostMatrixLayer_na(in_network_dataset=input_network,
out_network_analysis_layer=od_cost_matrix_layer,
impedance_attribute=impedance_attribute,
default_cutoff=str(cutoff_radius),
accumulate_attribute_name=accumulator_attributes,
UTurn_policy="ALLOW_UTURNS", hierarchy="NO_HIERARCHY",
output_path_shape="NO_LINES")
# Determine raster cell size
points_per_raster_cell = OD_MATRIX_ENTRIES / input_point_count
raster_cell_count = max(1, input_point_count / points_per_raster_cell)
input_points_extent = Describe(input_points).Extent
raster_cell_area = (input_points_extent.width * input_points_extent.height /
raster_cell_count)
raster_cell_size = int(sqrt(raster_cell_area))
# Construct |raster| from |input_points|
PointToRaster_conversion(in_features=input_points,
value_field=id_attribute, out_rasterdataset=raster,
cell_assignment="MOST_FREQUENT", priority_field="NONE",
cellsize=str(raster_cell_size))
# Construct |polygons| from |raster|
RasterToPolygon_conversion(in_raster=raster,
out_polygon_features=polygons, simplify="NO_SIMPLIFY",
raster_field="VALUE")
# Export empty |od_cost_matrix_lines| to |temp_dbf| to start adjacency list
TableToTable_conversion(in_rows=od_cost_matrix_lines,
out_path=output_location, out_name=temp_adj_dbf_name)
# Construct |polygons_layer| and |input_points_layer|
for (feature, layer) in [(polygons, polygons_layer),
(input_points, input_points_layer)]:
MakeFeatureLayer_management(in_features=feature, out_layer=layer)
def add_locations(sub_layer, field_mappings=""):
"""
|sub_layer|: one of "Origins", "Destinations", "Barrier Points"
|field_mappings|: field mappings in addition to those for "Name" and
"CurbApproach"
"""
AddLocations_na(in_network_analysis_layer=od_cost_matrix_layer,
sub_layer=sub_layer, in_table=input_points_layer,
field_mappings=("Name %s #; CurbApproach # 0; %s" %
(id_attribute, field_mappings)),
search_tolerance=SEARCH_TOLERANCE,
search_criteria=("%s SHAPE; %s SHAPE;" %
(junction_feature, edge_feature)),
append="CLEAR", snap_to_position_along_network="SNAP",
snap_offset=SNAP_OFFSET)
# OD cost matrix destinations
AddMessage(ADDING_DESTINATIONS_STARTED)
SelectLayerByLocation_management(in_layer=input_points_layer)
add_locations("Destinations")
AddMessage(ADDING_DESTINATIONS_FINISHED)
# OD cost matrix point barriers
AddMessage(ADDING_BARRIERS_STARTED)
add_locations("Point Barriers", ("FullEdge # 0; BarrierType # 2;"
"Attr_%s %s #;" % (impedance_attribute, trim(BARRIER_COST_FIELD))))
AddMessage(ADDING_BARRIERS_FINISHED)
# Compute adjacency list, one raster cell at a time
progress = Progress_Bar(raster_cell_count, 1, STEP_1)
rows = UpdateCursor(polygons)
for row in rows:
# Select the current polygon
SelectLayerByAttribute_management(in_layer_or_view=polygons_layer,
selection_type="NEW_SELECTION", where_clause="FID = %s" % str(row.FID))
# Origins
SelectLayerByLocation_management(in_layer=input_points_layer,
select_features=polygons_layer)
add_locations("Origins")
# Solve OD Cost matrix
Solve_na(in_network_analysis_layer=od_cost_matrix_layer,
ignore_invalids="SKIP")
# Add origin and destination fields to the adjacency list dbf
for (index, field) in [(0, ORIGIN_ID_FIELD_NAME),
(1, DESTINATION_ID_FIELD_NAME)]:
CalculateField_management(in_table=od_cost_matrix_lines,
field=field, expression="!Name!.split(' - ')[%d]" % index,
expression_type="PYTHON")
# Record actual distance between neighboring nodes
distance_field = "Total_%s" % impedance_attribute
CalculateField_management(in_table=od_cost_matrix_lines,
field=distance_field,
expression="!%s! - 2 * %d" % (distance_field, BARRIER_COST),
expression_type="PYTHON")
# Append result to |temp_adj_dbf|
TableToTable_conversion(in_rows=od_cost_matrix_lines,
out_path=auxiliary_dir, out_name=PARTIAL_ADJACENCY_LIST_NAME)
Append_management(inputs=partial_adj_dbf, target=temp_adj_dbf,
schema_type="TEST")
progress.step()
# Copy data from |temp_adj_dbf| to |adj_dbf|
Rename_management(in_data=temp_adj_dbf, out_data=adj_dbf)
# Clean up
for path in [od_cost_matrix_layer, partial_adj_dbf, polygons, raster,
polygons_layer, input_points_layer, auxiliary_dir]:
delete(path)
AddMessage(STEP_1_FAILED)
success = False
# Step 2
if success:
AddMessage(STEP_2_STARTED)
try:
distance_field = trim("Total_%s" % inputs[IMPEDANCE_ATTRIBUTE])
accumulator_fields = set([trim("Total_%s" % accumulator_attribute)
for accumulator_attribute in inputs[ACCUMULATOR_ATTRIBUTES].split(";")
if accumulator_attribute != "#"])
# Graph representation: dictionary mapping node id's to Node objects
nodes = {}
# The number of rows in |adj_dbf|
directed_edge_count = int(GetCount_management(adj_dbf).getOutput(0))
graph_progress = Progress_Bar(directed_edge_count, 1, STEP_2)
rows = UpdateCursor(adj_dbf)
for row in rows:
# Get neighboring nodes, and the distance between them
origin_id = row.getValue(trim(ORIGIN_ID_FIELD_NAME))
destination_id = row.getValue(trim(DESTINATION_ID_FIELD_NAME))
distance = float(row.getValue(distance_field))
# Make sure the nodes are recorded in the graph
for id in [origin_id, destination_id]:
if not id in nodes:
nodes[id] = Node()
# Make sure that the nodes are neighbors in the graph
if origin_id != destination_id and distance >= 0:
accumulations = {}
for field in accumulator_fields:
accumulations[field] = float(row.getValue(field))
