[Numpy-discussion] fast access and normalizing of ndarray slices
wkerzendorf at gmail.com
Thu May 31 01:36:07 EDT 2012
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.
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?
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