Comments (7)
Yes, for signal that has been sampled at a very low frequency, the local extrema can be misleading. I'd be happy if you'd send a PR. But I don't fully understand. If we are working on extrema of the splines, how do we construct the splines in the first place, since we need local extrema on the raw data to build the upper and lower envelopes?
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Hi, I mean that you can interpolate raw data by spline and interpolate the spline's extrema points for upper and lower envelopes.
here shows the difference between spline's local extrema and local extrema by index of array
http://docs.scipy.org/doc/scipy/reference/tutorial/interpolate.html#d-interpolation-interp1d
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All right. So we just add more samples in the raw data by interpolating it, and then perform sifting on this data. Is that right?
from pyhht.
No, adding more samples is needless, we can find exact extrema points on spline at x axis by first order derivatives' root and determine whether the points is maxima or minium by second order derivatives' sign(negative : maximum, positive : minimum)
http://docs.scipy.org/doc/scipy/reference/generated/scipy.interpolate.splder.html#scipy.interpolate.splder
http://docs.scipy.org/doc/scipy/reference/generated/scipy.interpolate.sproot.html#scipy.interpolate.sproot
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but why there's several files for the same purpose? which one should I modify?
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I sent pull request, please check
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Closing due to inactivity.
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Related Issues (20)
- Force stopping for complex signals HOT 9
- Instantaneous frequencies are not consistent with the plot of HHT HOT 10
- bivariate EMD has some bugs HOT 12
- preserving the decomposition memory HOT 2
- emd.py divide by zero & other uncaught exceptions HOT 2
- suggestion to add reference to pip HOT 4
- unnecessary print in plot ? HOT 1
- more meaningful representation of orthogonality HOT 12
- y labels rotation HOT 6
- more detailed ref to paper HOT 5
- computation of full Hilbert spectrum HOT 3
- EEMD algorithm HOT 1
- Clarification of boundary_conditions() example HOT 2
- EMD not stable while data rolling on HOT 1
- marginal spectrum and energy spectrum HOT 3
- According to which article
- I got some negative instantaneous frequencies HOT 2
- why this pyhht.emd diffrent with matlab 2018a emd result! HOT 5
- Docs do not build with Sphinx 4.0.2 HOT 4
- problem with tutorials
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