Function distance

pattern/vector/__init__.py:723–738

Returns the distance between two vectors.

(v1, v2, method=COSINE)

    "cosine", "euclidean", "manhattan", "hamming"
    
def distance(v1, v2, method=COSINE):
    """ Returns the distance between two vectors.
    """
    if method == COSINE:
        return 1 - cosine_similarity(v1, v2)
    if method == EUCLIDEAN: # Squared Euclidean distance is used (1.5x faster).
        return sum((v1.get(w, 0) - v2.get(w, 0)) ** 2 for w in set(chain(v1, v2)))
    if method == MANHATTAN:
        return sum(abs(v1.get(w, 0) - v2.get(w, 0)) for w in set(chain(v1, v2)))
    if method == HAMMING:
        d = sum(not (w in v1 and w in v2 and v1[w] == v2[w]) for w in set(chain(v1, v2))) 
        d = d / float(max(len(v1), len(v2)) or 1)
        return d
    if isinstance(method, type(distance)):
        # Given method is a function of the form: distance(v1, v2) => float.
        return method(v1, v2)

_distance  = distance