Thanks – sklearn works great!  I got exactly what I expected each time I ran it!

James

import sys

import numpy

from sklearn.cluster import *

print sys.version

vals = numpy.array([[0.0],[0.1],[0.5],[0.6],[1.0],[1.1]])

print vals

k_means_ex = KMeans(k=3)

x = k_means_ex.fit_predict(vals)

print x

print k_means_ex.cluster_centers_

print k_means_ex.score(vals)

2.7.3 (default, Apr 10 2012, 23:31:26) [MSC v.1500 32 bit (Intel)]

[[ 0. ]

[ 0.1]

[ 0.5]

[ 0.6]

[ 1. ]

[ 1.1]]

[1 1 0 0 2 2]

[[ 0.55]

[ 0.05]

[ 1.05]]

-0.015