Re: [eigen] Spline Fitting

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Hi Hauke!

On 13/04/12 13:21, Hauke Heibel wrote:
> Hi Class,
> I pushed your suggestion to the current development branch. There is
> now a second fitting function which allows you to provide the knot
> parameters.
Wow, that was fast.

> Thanks for trying out the module and for the feedback. Feel free to
> get back when you encounter other issues or possibilities for
> improvement.
Actually I have another question: I would like to interpolate 2d data on non-uniform grids, i.e.
I have data points

(x_i, y_i), i=1..n

and I would like to interpolate them onto a new x'-grid defined in terms of new nodes

x_j', j=1..m

As far as I understand, I have to calculate the parameter u_j of each new node x_j', right? How would
you do this?

Or is it possible to re-parameterise the spline with x as parameter (provided dx/du > 0, with  u
beeing the original spline parameter )?

Or are B-splines not the right tool for the job?


> Regrads,
> Hauke
> On Fri, Apr 13, 2012 at 10:10 AM, "Claas H. Köhler"
> <claas.koehler@xxxxxx> wrote:
>> Hi!
>> I just took a look at the unsupported Spline module, which seems to have a lot of potential. Taking a
>> look at the examples in the test rountines, I was wondering, whether it is mandatory to re-calculate
>> the chord lengths after a spline has been fitted to the data (this is the way it is done in the
>> examples).
>> As far as I understand, cord lenghts are needed to evaluate the spline at a defined node. So would it
>> be useful to maybe pass the cord lengths vector to the SplineFitting::Interpolate as parameter
>> instead of creating a temporary there? This way the user could access them after the spline has been
>> created.
>> Regards
>> Claas

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