On Fri, Jan 27, 2012 at 9:28 AM, Paul Anton Letnes <paul.anton.letnes@gmail.com> wrote:

On 27. jan. 2012, at 14:52, Chao YUE wrote:

> Dear all,
>
> suppose I have a ndarray a:
>
> In [66]: a
> Out[66]: array([0, 1, 2, 3, 4])
>
> how can use it as 5X1 array without doing a=a.reshape(5,1)?

Several ways, this is one, although not much simpler.
In [6]: a
Out[6]: array([0, 1, 2, 3, 4])

In [7]: a.shape = 5, 1

In [8]: a
Out[8]:
array([[0],
[1],
[2],
[3],
[4]])

Paul

I'm assuming your issue with that call to reshape is that you need to know the dimensions beforehand. An alternative is to call:

>>> a.reshape(-1, 1)

The "-1" allows numpy to "infer" the length based on the given sizes.

Another alternative is:

>>> a[:, np.newaxis]

-Tony