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

Stéfan van der Walt stefanv at berkeley.edu
Thu Apr 7 18:03:38 EDT 2016

On 7 April 2016 at 11:17, Chris Barker <chris.barker at noaa.gov> wrote:
> np.col_vector(arr)
> which would be a synonym for np.reshape(arr, (-1,1))
> would that make anyone happy?

I'm curious to see use cases where this doesn't solve the problem.

The most common operations that I run into:

colvec = lambda x: np.c_[x]

x = np.array([1, 2, 3])
A = np.arange(9).reshape((3, 3))

1) x @ x   (equivalent to x @ colvec(x))
2) A @ x  (equivalent to A @ colvec(x), apart from the shape)
3) x @ A
4) x @ colvec(x)  -- gives an error, but perhaps this should work and
be equivalent to np.dot(colvec(x), rowvec(x)) ?

If (4) were changed, 1D arrays would mostly* be interpreted as row
vectors, and there would be no need for a rowvec function.  And we
already do that kind of magic for (2).


* not for special case (1)

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