Re: [Help-gsl] HELP Please - Example of gsl_bspline_knots

[Patrick Alken]

Hi, if I understand your problem correctly, you should be able to use 
uniform knots. Non-uniform knots are useful when you have data that is 
not spread uniformly in your interval, for example if you have some x 
values clustered closely together, then a large gap of no x data, then 
another cluster, etc.

If your x data is spread somewhat nicely in your interval, just use 
uniform knots and the given example program should work for you if you 
just replace the input data with your own.

If your data is not very uniform and you have gaps in the data, then you 
should use non-uniform knots. Let me know if this is the case for you 
and I can provide further assistance.

Patrick

On 07/13/2010 03:16 PM, Atul D. Patil wrote:
> Hi,
>
> Anyone please can send/point me example program that uses gsl_bspline_knots
> function?
> The one GNU has given in user guide uses gsl_bspline_knots_uniform function.
>
> I am new to GSL and doing some research work using it. I've stuck over this
> problem for last few days
> and I tried few things but it didn't work.
>
> What I want to do is quite simple:
> I've intermittent X values which are not in any sequence (e.g. 6, 16, 28, 33,
> 46, 67, 76, 79, 86.. etc)
> and I've corresponding Y values (1280, 1302, 1325, 1295, 1187, 1123, 1024, 987,
> 865.. etc)
>
> All I want to do is computes a linear least squares fit to this data using cubic
> B-spline basis functions,
> so that I shall get output the smoothed curve of Y values. Also, for sequential
> X values (for e.g. values between
> 6 to 16 OR 16 to 28 in above example) I shall get corresponding Y values on the
> smoothed graph obtained by B-spline functions.
>
> I believe I need non-uniform knots to do this (I might be wrong. Please correct
> me if I am)
> Tell me if I can achieve this using uniform knots.
>
> In either case, example code would be greatly appreciated.
>
> Many thanks in anticipation,
> Atul D. Patil
>
>
>
>
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