sddspfit for high orders

Moderators: michael_borland, soliday

Post Reply
ksenia
Posts: 2
Joined: 11 Aug 2010, 09:45
Location: Novosibirsk, Russia

sddspfit for high orders

Post by ksenia » 14 Apr 2015, 04:41

Hello,

Function sddspfit seems to return incorrect result of fitting in some cases. Works well for polynomial orders 0,1,2 - but gives constant offset when I add orders of 3 and higher.
The example of data file and script attached (SL6 and SL7 were used)

Thank you!
Ksenia, BINP
Attachments
pfit_report.tar.gz
(461 Bytes) Downloaded 377 times

michael_borland
Posts: 1927
Joined: 19 May 2008, 09:33
Location: Argonne National Laboratory
Contact:

Re: sddspfit for high orders

Post by michael_borland » 14 Apr 2015, 08:22

Ksenia,

The problem is that the independent quantity (H6) has a large average value compared to its range. This causes numerical precision problems. You can fix this by adding the -autoOffset option, but should realize that the meaning of the fit coefficients is then changed.

--Michael

Post Reply