On Oct 13, 8:29 pm, Dale Dalrymple <d...@ieee.org> wrote: > On Oct 13, 8:22 am, Janto Dreijer <jan...@gmail.com> wrote: > > > I'm looking for code that will calculate the running median of a > > sequence, efficiently. (I'm trying to subtract the running median from > > a signal to correct for gradual drift). > > ... > > Any suggestions? > > For a reference try: > > Comparison of algorithms for standard median filtering > Juhola, M. Katajainen, J. Raita, T. > Signal Processing, IEEE Transactions on > Jan. 1991, Volume: 39 , Issue: 1, page(s): 204 - 208 > Abstract > > An algorithm I have used comes from: > > On computation of the running median > Astola, J.T. Campbell, T.G. > Acoustics, Speech and Signal Processing, IEEE Transactions on > Apr 1989, Volume: 37, Issue: 4, page(s): 572-574 > > This is a dual heap approach. No code though. There are some obvious > (yeah, right) errors in their pseudo-code. > > The point of the dual heap algorithm (loosely put) is to reduce the > computation to slide the window 1 element to be proportional to 2 > bubble sorts of log window size instead of a window size sort. > > Good luck. > > Dale B. Dalrymple
Thanks. I'll have a look. I found a PDF by Soumya D. Mohanty entitled "Efficient Algorithm for computing a Running Median" (2003) by Googling. It has code snippets at the end, but it's not going to be a simple cut-and-paste job. It will take some work figuring out the missing parts. Regards Janto -- http://mail.python.org/mailman/listinfo/python-list