[Numpy-discussion] indexing question

Robin robince@gmail....
Thu Mar 5 05:09:29 CST 2009


On Thu, Mar 5, 2009 at 10:57 AM, Robin <robince@gmail.com> wrote:
> On Thu, Mar 5, 2009 at 10:40 AM, Robin <robince@gmail.com> wrote:
>> Hi,
>>
>> I have an indexing problem, and I know it's a bit lazy to ask the
>> list, sometime when people do interesting tricks come up so I hope no
>> one minds!
>>
>> I have a 2D array X.shape = (a,b)
>>
>> and I want to change it into new array which is shape (2,(a*b)) which
>> has the following form:
>> [  X[0,0], X[0,1]
>>   X[1,0], X[1,1]
>>   X[2,0], X[2,1]
>>   ....
>>   X[a,0], X[a,1]
>>   X[0,1], X[0,2]
>>   X[1,1], X[1,2]
>> ...
>> ]
>>
>
> Ah, so it's a bit easier than I thought at first glance:
>
> X[ ix_( (b-1)*range(a), [0,1]) ]
> does the trick I think

Not doing well this morning - that's wrong of course...  I need to
stack lots of such blocks for [0,1], [1,2], [2,3] etc.. up to [b-1,b].
So I guess the question still stands...

Robin


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