I have a N-dimensional array A and I want to operate in one of the axis (k) with a 1 dimensional array (for instance, subtracting an array B of length k). I have looked for some solutions in the manual and did not found any.
I am not sure that I understand your problem exactly, but here's the solution to what I think your problem is ;-) from Scientific.indexing import index_expression import Numeric indices = index_expression[::] + \ (len(A.shape)-k-1)*index_expression[Numeric.NewAxis] result = A-B[indices] This uses a module from ScientificPython which provides syntactic sugar for indexing. In fact, the module is so simple that I include it here: --------------------------------------------------------------------------- # A nicer way to build up index tuples for arrays. # # You can do all this with slice() plus a few special objects, # but there's a lot to remember. This version is simpler because # it uses the standard array indexing syntax. # # Written by Konrad Hinsen <hinsen@cnrs-orleans.fr> # last revision: 1999-7-23 # """This module provides a convenient method for constructing array indices algorithmically. It provides one importable object, 'index_expression'. For any index combination, including slicing and axis insertion, 'a[indices]' is the same as 'a[index_expression[indices]]' for any array 'a'. However, 'index_expression[indices]' can be used anywhere in Python code and returns a tuple of indexing objects that can be used in the construction of complex index expressions. Sole restriction: Slices must be specified in the double-colon form, i.e. a[::] is allowed, whereas a[:] is not. """ class _index_expression_class: import sys maxint = sys.maxint def __getitem__(self, item): if type(item) != type(()): return (item,) else: return item def __len__(self): return self.maxint def __getslice__(self, start, stop): if stop == self.maxint: stop = None return self[start:stop:None] index_expression = _index_expression_class() --------------------------------------------------------------------------- Konrad. -- ------------------------------------------------------------------------------- Konrad Hinsen | E-Mail: hinsen@cnrs-orleans.fr Centre de Biophysique Moleculaire (CNRS) | Tel.: +33-2.38.25.56.24 Rue Charles Sadron | Fax: +33-2.38.63.15.17 45071 Orleans Cedex 2 | Deutsch/Esperanto/English/ France | Nederlands/Francais -------------------------------------------------------------------------------