[SciPy-User] Identify unique sequence data from array
Charles R Harris
Wed Dec 22 17:00:36 CST 2010
On Wed, Dec 22, 2010 at 2:51 PM, Robert Kern <firstname.lastname@example.org> wrote:
> On Wed, Dec 22, 2010 at 16:47, Paul Anton Letnes
> <email@example.com> wrote:
> > On 22. des. 2010, at 21.18, otrov wrote:
> >>>> The problem:
> >>>> I have 2D data sets (scipy/numpy arrays) of 10^7 to 10^8 rows, which
> consists of repeated sequences of one unique sequence, usually ~10^5 rows,
> but may differ in scale. Period is same for both columns, so there is not
> really difference if we consider 2D or 1D array.
> >>>> I want to track this data block.
> >>> for i in range(1, len(X)-1):
> >>> if (X[i:] == X[:-i]).all():
> >>> break
> >> Just look at that python beauty! Such a great language when in hand of a
> smart user.
> >> Thanks for you snippet, but unfortunately it takes forever to finish the
> > You could also check one element at a time. I think it will be faster,
> because it will break if comparison of the first element doesn't hold. Then,
> if you find such an occurrence, use Robert's method to double check that you
> found the true repetition period.
> Excellent point.
Why not do an FFT and look at the shape around the carrier frequency? The DC
level should probably be subtracted first. It shoud also be possible to
construct a Weiner filter to extract the sequences if they don't occur with
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