from math import sqrt
def l2(p):
return sqrt(sum((x**2 for x in p)))
# Pairwise distances between the elements of `points` with respect to some `norm`
class PairwiseDistances:
def __init__(self, points, norm = l2):
self.points = points
self.norm = norm
def __len__(self):
return len(self.points)
def __call__(self, p1, p2):
return self.norm((x - y for (x,y) in zip(self.points[p1], self.points[p2])))
# Caches all distances specified by `distances`
class ExplicitDistances:
def __init__(self, distances):
self.len = len(distances)
self.distances = []
for i in xrange(self.len):
self.distances.append([])
for j in xrange(self.len):
self.distances[-1].append(distances(i,j))
def __len__(self):
return self.len
def __call__(self, p1, p2):
return self.distances[p1][p2]
# Generator of all points in a file `filename` with one point per line
def points_file(filename):
fd = open(filename)
for line in fd.xreadlines():
if line.startswith('#'): continue
yield map(float, line.strip().split())
fd.close()