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% POLY_FIT: Warning: Invert detected a small pivot element - help needed [message #71353] Sat, 12 June 2010 11:54 Go to next message
sid is currently offline  sid
Messages: 50
Registered: January 1995
Member
Hi,
I am fitting my data with 3 degree polynomial using poly_fit,
after running the program, im getting this warning message % POLY_FIT:
Warning: Invert detected a small pivot element. Please suggest me if
there is any way to get rid of this and why exactly im getting this
kind of warning.
Note: I read from poly_fit help that by setting the /double keyword,
we can get rid of this kind of warning. But that doesn't helped me.
regards
sid
Re: % POLY_FIT: Warning: Invert detected a small pivot element - help needed [message #71694 is a reply to message #71353] Mon, 12 July 2010 16:41 Go to previous message
Craig Markwardt is currently offline  Craig Markwardt
Messages: 1869
Registered: November 1996
Senior Member
On Jul 11, 6:43 am, landsito <u...@compgroups.net/> wrote:
> Hi, I solved this with my code:
>
> poly_coefs = poly_fit(xvector, yvector, 3,/double,status=estatus)
>   if estatus eq 2 then begin
>       xvector=[0,xvector]
>       yvector=annularSum[xvector]
>       poly_coefs = poly_fit(xvector, yvector, 3,/double,status=estatus)
>       print, 'estatusss',estatus
>   endif
>
> Also, you can add more cases with a case 1: ....

It's not clear to me how adding fake data points will "solve" the
problem...
Re: % POLY_FIT: Warning: Invert detected a small pivot element - help needed [message #71709 is a reply to message #71353] Sun, 11 July 2010 03:52 Go to previous message
Giuseppe Papa is currently offline  Giuseppe Papa
Messages: 27
Registered: February 2010
Junior Member
Well, that error usually happens when the routine can't make the fit because the trend changes and you have few points so what you need to do is give it maybe one or two points more, so routine will know a better understanding to make the fitting.

Best regard,

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frmsrcurl: http://compgroups.net/comp.lang.idl-pvwave/-POLY_FIT-Warning -Invert-detected-a-small-pivot-element-help-needed
Re: % POLY_FIT: Warning: Invert detected a small pivot element - help needed [message #71710 is a reply to message #71353] Sun, 11 July 2010 03:43 Go to previous message
Giuseppe Papa is currently offline  Giuseppe Papa
Messages: 27
Registered: February 2010
Junior Member
Hi, I solved this with my code:

poly_coefs = poly_fit(xvector, yvector, 3,/double,status=estatus)
if estatus eq 2 then begin
xvector=[0,xvector]
yvector=annularSum[xvector]
poly_coefs = poly_fit(xvector, yvector, 3,/double,status=estatus)
print, 'estatusss',estatus
endif

Also, you can add more cases with a case 1: ....

Best regards.
Luis Navarro D.
luis.navarro.dominguez@gmail.com

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