[Numpy-discussion] fast access and normalizing of ndarray slices

Val Kalatsky kalatsky at gmail.com
Thu May 31 01:43:18 EDT 2012


What do you mean by "normalized it"?
Could you give the output of your procedure for the sample input data.
Val

On Thu, May 31, 2012 at 12:36 AM, Wolfgang Kerzendorf <wkerzendorf at gmail.com
> wrote:

> Dear all,
>
> I have an ndarray which consists of many arrays stacked behind each other
> (only conceptually, in truth it's a normal 1d float64 array).
> I have a second array which tells me the start of the individual data sets
> in the 1d float64 array and another one which tells me the length.
> Example:
>
> data_array = (conceptually) [[1,2], [1,2,3,4], [1,2,3]] = in reality
> [1,2,1,2,3,4,1,2,3, dtype=float64]
> start_pointer = [0, 2, 6]
> length_data = [2, 4, 3]
>
> I now want to normalize each of the individual data sets. I wrote a simple
> for loop over the start_pointer and length data grabbed the data and
> normalized it and wrote it back to the big array. That's slow. Is there an
> elegant numpy way to do that? Do I have to go the cython way?
>
> Cheers
>   Wolfgang
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