problems with duplicating and slicing an array

John Hunter jdhunter at
Thu Jan 20 22:51:11 EST 2005

>>>>> "Yun" == Yun Mao <yunmao at> writes:
    Yun> 2. Is there a way to do Matlab style slicing? e.g. if I have
    Yun> i = array([0, 2]) x = array([1.1, 2.2, 3.3, 4.4]) I wish y =
    Yun> x(i) would give me [1.1, 3.3] Now I'm using map, but it gets
    Yun> a little annoying when there are two dimensions.  Any ideas
    Yun> would be deeply appreciated!

numarray supports matlab style indexing if you pass the ind as an
array or list of indices (but not a tuple, I found to my surprise).
As pointed out already, for Numeric you need to use the take function

>>> from numarray import array
>>> x = array([1,2,3,4,5,6,7,8,9])
>>> ind = [3,5,7]
>>> inda = array(ind) 
>>> indt = tuple(ind)
>>> x[ind]
array([4, 6, 8])
>>> x[inda]
array([4, 6, 8])
>>> x[indt]
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
IndexError: too many indices.

I'm sure the tuple "surprise" is a documented feature.


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