diff options
Diffstat (limited to '.venv/lib/python3.12/site-packages/networkx/algorithms/triads.py')
| -rw-r--r-- | .venv/lib/python3.12/site-packages/networkx/algorithms/triads.py | 604 |
1 files changed, 604 insertions, 0 deletions
diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/triads.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/triads.py new file mode 100644 index 00000000..640fc304 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/triads.py @@ -0,0 +1,604 @@ +# See https://github.com/networkx/networkx/pull/1474 +# Copyright 2011 Reya Group <http://www.reyagroup.com> +# Copyright 2011 Alex Levenson <alex@isnotinvain.com> +# Copyright 2011 Diederik van Liere <diederik.vanliere@rotman.utoronto.ca> +"""Functions for analyzing triads of a graph.""" + +from collections import defaultdict +from itertools import combinations, permutations + +import networkx as nx +from networkx.utils import not_implemented_for, py_random_state + +__all__ = [ + "triadic_census", + "is_triad", + "all_triplets", + "all_triads", + "triads_by_type", + "triad_type", + "random_triad", +] + +#: The integer codes representing each type of triad. +#: +#: Triads that are the same up to symmetry have the same code. +TRICODES = ( + 1, + 2, + 2, + 3, + 2, + 4, + 6, + 8, + 2, + 6, + 5, + 7, + 3, + 8, + 7, + 11, + 2, + 6, + 4, + 8, + 5, + 9, + 9, + 13, + 6, + 10, + 9, + 14, + 7, + 14, + 12, + 15, + 2, + 5, + 6, + 7, + 6, + 9, + 10, + 14, + 4, + 9, + 9, + 12, + 8, + 13, + 14, + 15, + 3, + 7, + 8, + 11, + 7, + 12, + 14, + 15, + 8, + 14, + 13, + 15, + 11, + 15, + 15, + 16, +) + +#: The names of each type of triad. The order of the elements is +#: important: it corresponds to the tricodes given in :data:`TRICODES`. +TRIAD_NAMES = ( + "003", + "012", + "102", + "021D", + "021U", + "021C", + "111D", + "111U", + "030T", + "030C", + "201", + "120D", + "120U", + "120C", + "210", + "300", +) + + +#: A dictionary mapping triad code to triad name. +TRICODE_TO_NAME = {i: TRIAD_NAMES[code - 1] for i, code in enumerate(TRICODES)} + + +def _tricode(G, v, u, w): + """Returns the integer code of the given triad. + + This is some fancy magic that comes from Batagelj and Mrvar's paper. It + treats each edge joining a pair of `v`, `u`, and `w` as a bit in + the binary representation of an integer. + + """ + combos = ((v, u, 1), (u, v, 2), (v, w, 4), (w, v, 8), (u, w, 16), (w, u, 32)) + return sum(x for u, v, x in combos if v in G[u]) + + +@not_implemented_for("undirected") +@nx._dispatchable +def triadic_census(G, nodelist=None): + """Determines the triadic census of a directed graph. + + The triadic census is a count of how many of the 16 possible types of + triads are present in a directed graph. If a list of nodes is passed, then + only those triads are taken into account which have elements of nodelist in them. + + Parameters + ---------- + G : digraph + A NetworkX DiGraph + nodelist : list + List of nodes for which you want to calculate triadic census + + Returns + ------- + census : dict + Dictionary with triad type as keys and number of occurrences as values. + + Examples + -------- + >>> G = nx.DiGraph([(1, 2), (2, 3), (3, 1), (3, 4), (4, 1), (4, 2)]) + >>> triadic_census = nx.triadic_census(G) + >>> for key, value in triadic_census.items(): + ... print(f"{key}: {value}") + 003: 0 + 012: 0 + 102: 0 + 021D: 0 + 021U: 0 + 021C: 0 + 111D: 0 + 111U: 0 + 030T: 2 + 030C: 2 + 201: 0 + 120D: 0 + 120U: 0 + 120C: 0 + 210: 0 + 300: 0 + + Notes + ----- + This algorithm has complexity $O(m)$ where $m$ is the number of edges in + the graph. + + For undirected graphs, the triadic census can be computed by first converting + the graph into a directed graph using the ``G.to_directed()`` method. + After this conversion, only the triad types 003, 102, 201 and 300 will be + present in the undirected scenario. + + Raises + ------ + ValueError + If `nodelist` contains duplicate nodes or nodes not in `G`. + If you want to ignore this you can preprocess with `set(nodelist) & G.nodes` + + See also + -------- + triad_graph + + References + ---------- + .. [1] Vladimir Batagelj and Andrej Mrvar, A subquadratic triad census + algorithm for large sparse networks with small maximum degree, + University of Ljubljana, + http://vlado.fmf.uni-lj.si/pub/networks/doc/triads/triads.pdf + + """ + nodeset = set(G.nbunch_iter(nodelist)) + if nodelist is not None and len(nodelist) != len(nodeset): + raise ValueError("nodelist includes duplicate nodes or nodes not in G") + + N = len(G) + Nnot = N - len(nodeset) # can signal special counting for subset of nodes + + # create an ordering of nodes with nodeset nodes first + m = {n: i for i, n in enumerate(nodeset)} + if Nnot: + # add non-nodeset nodes later in the ordering + not_nodeset = G.nodes - nodeset + m.update((n, i + N) for i, n in enumerate(not_nodeset)) + + # build all_neighbor dicts for easy counting + # After Python 3.8 can leave off these keys(). Speedup also using G._pred + # nbrs = {n: G._pred[n].keys() | G._succ[n].keys() for n in G} + nbrs = {n: G.pred[n].keys() | G.succ[n].keys() for n in G} + dbl_nbrs = {n: G.pred[n].keys() & G.succ[n].keys() for n in G} + + if Nnot: + sgl_nbrs = {n: G.pred[n].keys() ^ G.succ[n].keys() for n in not_nodeset} + # find number of edges not incident to nodes in nodeset + sgl = sum(1 for n in not_nodeset for nbr in sgl_nbrs[n] if nbr not in nodeset) + sgl_edges_outside = sgl // 2 + dbl = sum(1 for n in not_nodeset for nbr in dbl_nbrs[n] if nbr not in nodeset) + dbl_edges_outside = dbl // 2 + + # Initialize the count for each triad to be zero. + census = {name: 0 for name in TRIAD_NAMES} + # Main loop over nodes + for v in nodeset: + vnbrs = nbrs[v] + dbl_vnbrs = dbl_nbrs[v] + if Nnot: + # set up counts of edges attached to v. + sgl_unbrs_bdy = sgl_unbrs_out = dbl_unbrs_bdy = dbl_unbrs_out = 0 + for u in vnbrs: + if m[u] <= m[v]: + continue + unbrs = nbrs[u] + neighbors = (vnbrs | unbrs) - {u, v} + # Count connected triads. + for w in neighbors: + if m[u] < m[w] or (m[v] < m[w] < m[u] and v not in nbrs[w]): + code = _tricode(G, v, u, w) + census[TRICODE_TO_NAME[code]] += 1 + + # Use a formula for dyadic triads with edge incident to v + if u in dbl_vnbrs: + census["102"] += N - len(neighbors) - 2 + else: + census["012"] += N - len(neighbors) - 2 + + # Count edges attached to v. Subtract later to get triads with v isolated + # _out are (u,unbr) for unbrs outside boundary of nodeset + # _bdy are (u,unbr) for unbrs on boundary of nodeset (get double counted) + if Nnot and u not in nodeset: + sgl_unbrs = sgl_nbrs[u] + sgl_unbrs_bdy += len(sgl_unbrs & vnbrs - nodeset) + sgl_unbrs_out += len(sgl_unbrs - vnbrs - nodeset) + dbl_unbrs = dbl_nbrs[u] + dbl_unbrs_bdy += len(dbl_unbrs & vnbrs - nodeset) + dbl_unbrs_out += len(dbl_unbrs - vnbrs - nodeset) + # if nodeset == G.nodes, skip this b/c we will find the edge later. + if Nnot: + # Count edges outside nodeset not connected with v (v isolated triads) + census["012"] += sgl_edges_outside - (sgl_unbrs_out + sgl_unbrs_bdy // 2) + census["102"] += dbl_edges_outside - (dbl_unbrs_out + dbl_unbrs_bdy // 2) + + # calculate null triads: "003" + # null triads = total number of possible triads - all found triads + total_triangles = (N * (N - 1) * (N - 2)) // 6 + triangles_without_nodeset = (Nnot * (Nnot - 1) * (Nnot - 2)) // 6 + total_census = total_triangles - triangles_without_nodeset + census["003"] = total_census - sum(census.values()) + + return census + + +@nx._dispatchable +def is_triad(G): + """Returns True if the graph G is a triad, else False. + + Parameters + ---------- + G : graph + A NetworkX Graph + + Returns + ------- + istriad : boolean + Whether G is a valid triad + + Examples + -------- + >>> G = nx.DiGraph([(1, 2), (2, 3), (3, 1)]) + >>> nx.is_triad(G) + True + >>> G.add_edge(0, 1) + >>> nx.is_triad(G) + False + """ + if isinstance(G, nx.Graph): + if G.order() == 3 and nx.is_directed(G): + if not any((n, n) in G.edges() for n in G.nodes()): + return True + return False + + +@not_implemented_for("undirected") +@nx._dispatchable +def all_triplets(G): + """Returns a generator of all possible sets of 3 nodes in a DiGraph. + + .. deprecated:: 3.3 + + all_triplets is deprecated and will be removed in NetworkX version 3.5. + Use `itertools.combinations` instead:: + + all_triplets = itertools.combinations(G, 3) + + Parameters + ---------- + G : digraph + A NetworkX DiGraph + + Returns + ------- + triplets : generator of 3-tuples + Generator of tuples of 3 nodes + + Examples + -------- + >>> G = nx.DiGraph([(1, 2), (2, 3), (3, 4)]) + >>> list(nx.all_triplets(G)) + [(1, 2, 3), (1, 2, 4), (1, 3, 4), (2, 3, 4)] + + """ + import warnings + + warnings.warn( + ( + "\n\nall_triplets is deprecated and will be removed in v3.5.\n" + "Use `itertools.combinations(G, 3)` instead." + ), + category=DeprecationWarning, + stacklevel=4, + ) + triplets = combinations(G.nodes(), 3) + return triplets + + +@not_implemented_for("undirected") +@nx._dispatchable(returns_graph=True) +def all_triads(G): + """A generator of all possible triads in G. + + Parameters + ---------- + G : digraph + A NetworkX DiGraph + + Returns + ------- + all_triads : generator of DiGraphs + Generator of triads (order-3 DiGraphs) + + Examples + -------- + >>> G = nx.DiGraph([(1, 2), (2, 3), (3, 1), (3, 4), (4, 1), (4, 2)]) + >>> for triad in nx.all_triads(G): + ... print(triad.edges) + [(1, 2), (2, 3), (3, 1)] + [(1, 2), (4, 1), (4, 2)] + [(3, 1), (3, 4), (4, 1)] + [(2, 3), (3, 4), (4, 2)] + + """ + triplets = combinations(G.nodes(), 3) + for triplet in triplets: + yield G.subgraph(triplet).copy() + + +@not_implemented_for("undirected") +@nx._dispatchable +def triads_by_type(G): + """Returns a list of all triads for each triad type in a directed graph. + There are exactly 16 different types of triads possible. Suppose 1, 2, 3 are three + nodes, they will be classified as a particular triad type if their connections + are as follows: + + - 003: 1, 2, 3 + - 012: 1 -> 2, 3 + - 102: 1 <-> 2, 3 + - 021D: 1 <- 2 -> 3 + - 021U: 1 -> 2 <- 3 + - 021C: 1 -> 2 -> 3 + - 111D: 1 <-> 2 <- 3 + - 111U: 1 <-> 2 -> 3 + - 030T: 1 -> 2 -> 3, 1 -> 3 + - 030C: 1 <- 2 <- 3, 1 -> 3 + - 201: 1 <-> 2 <-> 3 + - 120D: 1 <- 2 -> 3, 1 <-> 3 + - 120U: 1 -> 2 <- 3, 1 <-> 3 + - 120C: 1 -> 2 -> 3, 1 <-> 3 + - 210: 1 -> 2 <-> 3, 1 <-> 3 + - 300: 1 <-> 2 <-> 3, 1 <-> 3 + + Refer to the :doc:`example gallery </auto_examples/graph/plot_triad_types>` + for visual examples of the triad types. + + Parameters + ---------- + G : digraph + A NetworkX DiGraph + + Returns + ------- + tri_by_type : dict + Dictionary with triad types as keys and lists of triads as values. + + Examples + -------- + >>> G = nx.DiGraph([(1, 2), (1, 3), (2, 3), (3, 1), (5, 6), (5, 4), (6, 7)]) + >>> dict = nx.triads_by_type(G) + >>> dict["120C"][0].edges() + OutEdgeView([(1, 2), (1, 3), (2, 3), (3, 1)]) + >>> dict["012"][0].edges() + OutEdgeView([(1, 2)]) + + References + ---------- + .. [1] Snijders, T. (2012). "Transitivity and triads." University of + Oxford. + https://web.archive.org/web/20170830032057/http://www.stats.ox.ac.uk/~snijders/Trans_Triads_ha.pdf + """ + # num_triads = o * (o - 1) * (o - 2) // 6 + # if num_triads > TRIAD_LIMIT: print(WARNING) + all_tri = all_triads(G) + tri_by_type = defaultdict(list) + for triad in all_tri: + name = triad_type(triad) + tri_by_type[name].append(triad) + return tri_by_type + + +@not_implemented_for("undirected") +@nx._dispatchable +def triad_type(G): + """Returns the sociological triad type for a triad. + + Parameters + ---------- + G : digraph + A NetworkX DiGraph with 3 nodes + + Returns + ------- + triad_type : str + A string identifying the triad type + + Examples + -------- + >>> G = nx.DiGraph([(1, 2), (2, 3), (3, 1)]) + >>> nx.triad_type(G) + '030C' + >>> G.add_edge(1, 3) + >>> nx.triad_type(G) + '120C' + + Notes + ----- + There can be 6 unique edges in a triad (order-3 DiGraph) (so 2^^6=64 unique + triads given 3 nodes). These 64 triads each display exactly 1 of 16 + topologies of triads (topologies can be permuted). These topologies are + identified by the following notation: + + {m}{a}{n}{type} (for example: 111D, 210, 102) + + Here: + + {m} = number of mutual ties (takes 0, 1, 2, 3); a mutual tie is (0,1) + AND (1,0) + {a} = number of asymmetric ties (takes 0, 1, 2, 3); an asymmetric tie + is (0,1) BUT NOT (1,0) or vice versa + {n} = number of null ties (takes 0, 1, 2, 3); a null tie is NEITHER + (0,1) NOR (1,0) + {type} = a letter (takes U, D, C, T) corresponding to up, down, cyclical + and transitive. This is only used for topologies that can have + more than one form (eg: 021D and 021U). + + References + ---------- + .. [1] Snijders, T. (2012). "Transitivity and triads." University of + Oxford. + https://web.archive.org/web/20170830032057/http://www.stats.ox.ac.uk/~snijders/Trans_Triads_ha.pdf + """ + if not is_triad(G): + raise nx.NetworkXAlgorithmError("G is not a triad (order-3 DiGraph)") + num_edges = len(G.edges()) + if num_edges == 0: + return "003" + elif num_edges == 1: + return "012" + elif num_edges == 2: + e1, e2 = G.edges() + if set(e1) == set(e2): + return "102" + elif e1[0] == e2[0]: + return "021D" + elif e1[1] == e2[1]: + return "021U" + elif e1[1] == e2[0] or e2[1] == e1[0]: + return "021C" + elif num_edges == 3: + for e1, e2, e3 in permutations(G.edges(), 3): + if set(e1) == set(e2): + if e3[0] in e1: + return "111U" + # e3[1] in e1: + return "111D" + elif set(e1).symmetric_difference(set(e2)) == set(e3): + if {e1[0], e2[0], e3[0]} == {e1[0], e2[0], e3[0]} == set(G.nodes()): + return "030C" + # e3 == (e1[0], e2[1]) and e2 == (e1[1], e3[1]): + return "030T" + elif num_edges == 4: + for e1, e2, e3, e4 in permutations(G.edges(), 4): + if set(e1) == set(e2): + # identify pair of symmetric edges (which necessarily exists) + if set(e3) == set(e4): + return "201" + if {e3[0]} == {e4[0]} == set(e3).intersection(set(e4)): + return "120D" + if {e3[1]} == {e4[1]} == set(e3).intersection(set(e4)): + return "120U" + if e3[1] == e4[0]: + return "120C" + elif num_edges == 5: + return "210" + elif num_edges == 6: + return "300" + + +@not_implemented_for("undirected") +@py_random_state(1) +@nx._dispatchable(preserve_all_attrs=True, returns_graph=True) +def random_triad(G, seed=None): + """Returns a random triad from a directed graph. + + .. deprecated:: 3.3 + + random_triad is deprecated and will be removed in version 3.5. + Use random sampling directly instead:: + + G.subgraph(random.sample(list(G), 3)) + + Parameters + ---------- + G : digraph + A NetworkX DiGraph + seed : integer, random_state, or None (default) + Indicator of random number generation state. + See :ref:`Randomness<randomness>`. + + Returns + ------- + G2 : subgraph + A randomly selected triad (order-3 NetworkX DiGraph) + + Raises + ------ + NetworkXError + If the input Graph has less than 3 nodes. + + Examples + -------- + >>> G = nx.DiGraph([(1, 2), (1, 3), (2, 3), (3, 1), (5, 6), (5, 4), (6, 7)]) + >>> triad = nx.random_triad(G, seed=1) + >>> triad.edges + OutEdgeView([(1, 2)]) + + """ + import warnings + + warnings.warn( + ( + "\n\nrandom_triad is deprecated and will be removed in NetworkX v3.5.\n" + "Use random.sample instead, e.g.::\n\n" + "\tG.subgraph(random.sample(list(G), 3))\n" + ), + category=DeprecationWarning, + stacklevel=5, + ) + if len(G) < 3: + raise nx.NetworkXError( + f"G needs at least 3 nodes to form a triad; (it has {len(G)} nodes)" + ) + nodes = seed.sample(list(G.nodes()), 3) + G2 = G.subgraph(nodes) + return G2 |