| ''' |
| altgraph.GraphStat - Functions providing various graph statistics |
| ================================================================= |
| ''' |
| import sys |
| |
| 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 |
| out_points = 0 |
| for value in values: |
| try: |
| if (value - min_val) < 0: |
| out_points += 1 |
| else: |
| index = int((value - min_val)/float(bin_size)) |
| bins[index] += 1 |
| except IndexError: |
| out_points += 1 |
| |
| # 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 |
