comp.lang.idl-pvwave archive: archive » Re: Piecewise curve fitting in idl

Home » Public Forums » archive » Re: Piecewise curve fitting in idl

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Piecewise curve fitting in idl [message #61781 is a reply to message #61779]

Thu, 31 July 2008 07:41

pgrigis
Messages: 436
Registered: September 2007

Senior Member

d.po...@gmail.com wrote:
> On 31 Jul., 05:39, James Kuyper <jameskuy...@verizon.net> wrote:
>> d.po...@gmail.com wrote:
>>> On Jul 31, 1:21 pm, Wox <nom...@hotmail.com> wrote:
>>>> On Thu, 31 Jul 2008 03:30:22 -0700 (PDT), d.po...@gmail.com wrote:
>>>> > Folks
>>>> > How we can do the piecewise curve fitting in idl. Say we have an array
>>>> > that this array has got 2 or 3 trends in data and we want to fit a
>>>> > liner curve for each trends. In MATLAB curve fitting tool, we can
>>>> > easily exclude or include a part of data and then fit a curve. How we
>>>> > can do this in IDL
>>>> > Cheers
>>>> > Dave
>>>> Euhm, just do the fitting on the different parts? Or do you mean
>>>> fitting with a piecewise polynomial (i.e. spline: see e.g. IMSL_BSLSQ
>>>> or IMSL_CONLSQ)
>>
>>> just doing the fitting on the difrent part. how we can select this
>>> parts and how we can fit a curve to these parts separatly?
>>> Cheers
>>
>> Identifying the different parts is up to you. How do you know that there
>> are 2-3 different trends? Whatever method you use to reach that
>> conclusion will have to be adequate to identify where the different
>> trends start and end. However, once you have identified the different
>> parts you want fit separately, fitting each one separately is trivial:
>> pass x[trend_start[i]:trend_end[i]] and y[trend_start[i]:trend_end[i]]
>> to the curve-fitting routine.
>>
>> If you want a curve fitting routine that automatically figures out where
>> each trend starts and ends, then it gets a LOT more complicated. You
>> could do that by using a non-linear curve fitting routine, and make the
>> transition point between the two trends be one of the parameters of your
>> fitting curve. However, I would strongly recommend trying to understand
>> why you see 2 or 3 different trends, and then try to come up with a
>> single mathematical model for the entire curve that reflects that
>> reason. Then fit that model to your data.- Zitierten Text ausblenden -
>>
>> - Zitierten Text anzeigen -
>
> how we can do this in Iplot?

how can we tighten a screw with a toothbrush?

Paolo

Report message to a moderator

[Message index]

		Re: Piecewise curve fitting in idl By: Wox on Fri, 01 August 2008 01:27
		Re: Piecewise curve fitting in idl By: jameskuyper on Thu, 31 July 2008 07:58
		Re: Piecewise curve fitting in idl By: pgrigis on Thu, 31 July 2008 07:41
		Re: Piecewise curve fitting in idl By: Paul Van Delst[1] on Thu, 31 July 2008 07:31
		Re: Piecewise curve fitting in idl By: David Fanning on Thu, 31 July 2008 07:03
		Re: Piecewise curve fitting in idl By: d.poreh on Thu, 31 July 2008 07:00
		Re: Piecewise curve fitting in idl By: jameskuyper on Thu, 31 July 2008 05:39
		Re: Piecewise curve fitting in idl By: d.poreh on Thu, 31 July 2008 04:54
		Re: Piecewise curve fitting in idl By: Wox on Thu, 31 July 2008 04:21
		Re: Piecewise curve fitting in idl By: Craig Markwardt on Sun, 03 August 2008 21:58

Previous Topic:	Re: Surface fitting image with missing data
Next Topic:	Re: Edge detection and convert edges into polygons

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Sat Oct 11 07:20:42 PDT 2025

Total time taken to generate the page: 0.87771 seconds