[Numpy-discussion] r_, c_, hstack, and vstack with 1-d arrays

Bill Baxter wbaxter at gmail.com
Fri Jul 21 07:22:18 CDT 2006


On 7/21/06, Sven Schreiber <svetosch at gmx.net> wrote:
> Bill Baxter schrieb:
>
> > Finally, I noticed that the atleast_nd methods return arrays
> > regardless of input type.
>
> Are you sure? I reported that issue with *stack and I remember it was fixed.

Doh! My bad.  You're right.  I was looking at the code in SVN for the
atleast_* methods
and didn't realize that the array constructor (or any constructor)
could actually return something besides an object of that class.  But
that's exactly what array(subok=True) allows.

> > SUMMARY:
> > * make r_ behave like "vstack plus range literals"
> > * make column_stack only transpose its 1d inputs.
> > * rename r_,c_ to v_,h_ (or something else) to make their connection
> > with vstack and hstack clearer.  Maybe vs_ and hs_ would be better?
> > * make a new vertsion of 'c_' that acts like column_stack so that
> > theres a nice parallel v_<=>vstack,  h_<=>hstack, c_<=>column_stack
> > * make atleast_*d methods preserve the input type whenever possible
> >
>
> One problem with all that renaming is the other (maybe more important)
> function of r_: build (array or) matrix ranges quickly.

How would you duplicate this kind of behavior, you mean?
>>>   r_[1:4,0,4]
array([1, 2, 3, 0, 4])

That's what h_ would do.  Just as if you had done hstack( (range(1,4),0,4) ).

That's actually a good reason for the renaming/retooling.  r_ is kind
of schitzophrenic now in that it acts *either* as "concatenate rows
(vstack-like, for >=2-d)" or "build me a row (hstack-like, for <2d)".
So it's hard to remember what the 'r' in r_ stands for.  On the other
hand, c_ is always hstack-like.

By the way, I noticed that 'row_stack' has appeared as a synonym for
'vstack' in SVN.  Thanks to whomever added it!

--bb




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