There's a numpy.abs but no numpy.matlib.abs.
>> import numpy as N
>> import numpy.matlib as M
>>
>> N.abs?
Type: ufunc
Base Class: <type 'numpy.ufunc'>
String Form: <ufunc 'absolute'>
Namespace: Interactive
Docstring:
y = absolute(x) takes |x| elementwise.
>> M.abs?
Object `M.abs` not found.