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"""
altgraph.GraphStat - Functions providing various graph statistics
=================================================================
"""
def degree_dist(graph, limits=(0, 0), bin_num=10, mode="out"):
"""
Computes the degree distribution for a graph.
Returns a list of tuples where the first element of the tuple is the
center of the bin representing a range of degrees and the second element
of the tuple are the number of nodes with the degree falling in the range.
Example::
....
"""
deg = []
if mode == "inc":
get_deg = graph.inc_degree
else:
get_deg = graph.out_degree
for node in graph:
deg.append(get_deg(node))
if not deg:
return []
results = _binning(values=deg, limits=limits, bin_num=bin_num)
return results
_EPS = 1.0 / (2.0 ** 32)
def _binning(values, limits=(0, 0), bin_num=10):
"""
Bins data that falls between certain limits, if the limits are (0, 0) the
minimum and maximum values are used.
Returns a list of tuples where the first element of the tuple is the
center of the bin and the second element of the tuple are the counts.
"""
if limits == (0, 0):
min_val, max_val = min(values) - _EPS, max(values) + _EPS
else:
min_val, max_val = limits
# get bin size
bin_size = (max_val - min_val) / float(bin_num)
bins = [0] * (bin_num)
# will ignore these outliers for now
for value in values:
try:
if (value - min_val) >= 0:
index = int((value - min_val) / float(bin_size))
bins[index] += 1
except IndexError:
pass
# make it ready for an x,y plot
result = []
center = (bin_size / 2) + min_val
for i, y in enumerate(bins):
x = center + bin_size * i
result.append((x, y))
return result
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