[Numpy-discussion] Indexing and lookup issues

Ross Williamson rosswilliamson.spt@gmail....
Wed Sep 22 15:46:52 CDT 2010


Thank you Anne

I was doing something totally stupid at my end.

Ross

On Wed, Sep 22, 2010 at 3:42 PM, Anne Archibald
<aarchiba@physics.mcgill.ca> wrote:
> On 22 September 2010 16:38, Ross Williamson
> <rosswilliamson.spt@gmail.com> wrote:
>> Hi everyone
>>
>> I suspect this is easy but I'm stuck
>>
>> say I have a 1D array:
>>
>> t = [10,11,12]
>>
>> and a 2D array:
>>
>> id = [[0,1,0]
>> [0,2,0]
>> [2,0,2]]
>>
>> In could in IDL do y = t[id] which would produce:
>>
>> y = [[10,11,10]
>> [10,12,10]
>> [12,10,12]]
>>
>> i.e. use the indexes in id on the lookup array t.
>>
>> Is there an easy way to do this in numpy?
>
> In [1]: t = np.array([10,11,12])
>
> In [2]: id = np.array([[0,1,0], [0,2,0], [2,0,2]])
>
> In [3]: t[id]
> Out[3]:
> array([[10, 11, 10],
>       [10, 12, 10],
>       [12, 10, 12]])
>
> Anne
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-- 
Ross Williamson
University of Chicago
Department of Astronomy & Astrophysics
773-834-9785 (office)
312-504-3051 (Cell)


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