The chirp challenge was proposed by Mathsoft [DAEP, 2003].
Conventional smoothers [most known ones] fail miserably.

3 methods do recover the signal:

1. Robert Advanced LSQ [a supplementary step to this basic one]
2. Spline_2xV6 [independent freeware software]
3. linfitCheby. Smath delights crunching "linfitCheby".

Jean



Polynomial fit CELL Copy.sm (230 KiB) downloaded 60 time(s).