[Numpy-discussion] Status of numeric3 / scipylite / scipy_core

Paul Barrett barrett at stsci.edu
Fri Mar 18 07:23:08 CST 2005


Tim Hochberg wrote:

>
> My take is that having even one type of index array overloaded onto 
> the current indexing scheme is questionable. In fact, even numarray's 
> current scheme is too complicated for my taste. I particularly don't 
> like the distinction that has to be made between lists and arrays on 
> one side and tuples on the other. I understand why it's there, but I 
> don't like it.
>
> Is it really necessary to pile these indexing schemes directly onto 
> the main array object. It seems that it would be clearer, and more 
> flexible, to use a separate, attached adapter object. For instance 
> (please excuse the names as I don't have good ideas for those):
>
> X.rows[ind0, ind1, ..., ind2, :]
>
> would act like take(take(take(X, ind0, 0), ind1, 1), ind2, -1)). That 
> is it would select the rows given by ind0 along the 0th axis, the rows 
> given by ind1 along the 1st axis (aka the columns) and the rows given 
> by ind2 along the -2nd axis.
>
> X.atindex[indices] would give  numarray's current indexarray behaviour.
>
> Etc, etc for any other indexing scheme that's deemed useful.
>
> As I think about it more I'm more convinced that basic indexing should 
> not support index arrays at all. Any indexarray behaviour should be 
> impleented using helper/adapter objects. Keep basic indexing simple. 
> This also gives an opportunity to have multiple different types of 
> index arrays behaviour.

So you're saying that 1-D indexing arrays (or vectors) should not be 
allowed?  As Perry said earlier, 'slice(1,9,2)' is equivalent to 
'range(1, 9, 2)'.  I just consider slices to be a shorthand for 
_regular_ indexing, whereas indexed arrays also allow for _irregular_ 
indexing.  Or am I missing something?

 -- Paul

-- 
Paul Barrett, PhD      Space Telescope Science Institute
Phone: 410-338-4475    ESS/Science Software Branch
FAX:   410-338-4767    Baltimore, MD 21218





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