[AstroPy] Linearity correction by polynomial fitting

James Turner jturner@gemini....
Thu Apr 18 14:03:39 CDT 2013


Good.

Tim Pickering also said that "something like scipy.optimize.fmin_powell"
will handle vectors of coefficients so you can vectorize the whole thing
but I think he forgot to copy you...

James.


On 18/04/13 15:00, Joe Philip Ninan wrote:
> Hi James,
> I think i shall try to keep the code as much pure python as possible. Installing
> iraf on the controller machine just for one routine will probably be an over kill.
> Nadia sent me link to pull request of astropy which can do fitting on 2d array.
> So i only have to flatten by 3d to a 2d, with time along the column. (
> https://github.com/astropy/astropy/pull/493 ).
> This isn't merged to astropy yet, but i was told it will be merged soon.
> Thanks for the suggestions,
> -cheers
> joe
>
>
> On 18 April 2013 22:49, James Turner <jturner@gemini.edu
> <mailto:jturner@gemini.edu>> wrote:
>
>      > But I couldn't find anything for fitting a polynomial for every pixel
>     along an
>      > axis of an ndarray.
>      > Is there a tool to do this? Without implementing a python loop to loop
>     through
>      > each pixel and calculate coefficients?
>
>     I'm not sure if there is anything yet (could tell you how to do
>     it in IRAF), as I think fitting has been a bit of a missing area
>     in Python until some recent work-in-progress. But wouldn't it
>     help to use Cython? I was also wondering whether a Python loop
>     will really be that slow if you're doing something relatively
>     non-trivial like a fit, but it probably will be since the axis
>     you're fitting will be much shorter than the image size...
>
>     Cheers,
>
>     James.
>
>
>      > Worst case scenario, i think i will have to write a C routine to do
>     polynomial
>      > fit and call it from python. But i would really love if a pure python
>      > alternative exists.
>      >
>      > Thanks
>      > -cheers
>      > joe
>      >
>      >
>      >
>      >
>      >
>      > --
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>      >
>      > ************************************************
>      > Joe Philip Ninan http://sites.google.com/site/jpninan/
>      > Research Scholar        /________________\
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> --
> /---------------------------------------------------------------
> "GNU/Linux: because a PC is a terrible thing to waste" -  GNU Generation
>
> ************************************************
> Joe Philip Ninan http://sites.google.com/site/jpninan/
> Research Scholar        /________________\
> DAA,                            | Vadakeparambil |
> TIFR,                           | Pullad P.O.         |
> Mumbai-05, India.      | Kerala, India      |
> Ph: +917738438212   | PIN:689548       |
> ------------------------------\_______________/--------------



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