[Numpy-discussion] ndarray.T2 for 2D transpose

Todd toddrjen at gmail.com
Wed Apr 6 13:39:49 EDT 2016


I would make `arr.T2` the same as `np.atleast_2d(arr).T`.  So a 1D array
would act as a row vector, since that is already the convention for
coercing 1D arrays to 2D.

On Tue, Apr 5, 2016 at 10:49 PM, Juan Nunez-Iglesias <jni.soma at gmail.com>
wrote:

> Todd,
>
> Would you consider a 1D array to be a row vector or a column vector for
> the purposes of transposition? The "correct" answer is not clear to me.
>
> Juan.
>
> On Wed, Apr 6, 2016 at 12:26 PM, Alan Isaac <alan.isaac at gmail.com> wrote:
>
>> On 4/5/2016 10:11 PM, Todd wrote:
>>
>>> When you try to transpose a 1D array, it does nothing.  This is the
>>> correct behavior, since it transposing a 1D array is meaningless.
>>> However, this can often lead to unexpected errors since this is rarely
>>> what you want.  You can convert the array to 2D, using `np.atleast_2d`
>>> or `arr[None]`, but this makes simple linear algebra computations more
>>> difficult.
>>>
>>> I propose adding an argument to transpose, perhaps called `expand` or
>>> `expanddim`, which if `True` (it is `False` by default) will force the
>>> array to be at least 2D.  A shortcut property, `ndarray.T2`, would be
>>> the same as `ndarray.transpose(True)`.
>>>
>>
>>
>>
>> Use `dot`.  E.g.,
>>         m.dot(a)
>>
>> hth,
>> Alan Isaac
>>
>>
>>
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>
>
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