# Re: 3D interpolation

From: Jean-Eric Campagne <campagne_at_lal.in2p3.fr>
Date: Tue, 26 Apr 2005 13:11:16 +0200

Hello Otto,
My problem is highly non gaussian and the Chi2 presents 2 local minimum reflecting the ambiguity of the physics involved. I will use some hints given by Rene and see if I can manage.
See you
Jean-Eric

--On mardi 26 avril 2005 12:43 +0200 Otto Schaile <Otto.Schaile_at_Physik.Uni-Muenchen.DE> wrote:

> Hi Jean-Eric,
>
> I would try to fit a TF2 (2-dim function) to the x,y, chi2 values
> and then plot this function. The question is if you find a simple
> function. Polynomials with high enough degree fit of course
> everything.
> If you want I can provide you with a simple 2 dim gauss.
> When plotting the function you can adjust the number of contours
> and the level heights by calls to:
>
> f1->SetContour(Int_t nlevels, const Double_t *levels)
>
> Cheers
> Otto
>
> On Tue, 26 Apr 2005, Jean-Eric Campagne wrote:
>
>> Dear developpers,
>>
>> I wander if you can help me in the following task: my final goal is to
>> plot Chi2 contours in a 2 dimentions x-y plot.
>>
>> As a starting point, I have a table of Chi2_ij values for some (x_i, y_j)
>> points. The contours are the location of (x,y) points where Chi2(x,y) =
>> 10.64 (for definiteness).
>>
>> My problem is to get the (x,y) location that fullfill the above
>> constraint, for that the Chi2 should be evaluated (interpolated) between
>> the different (x_i,y_j,Chi2_ij) values.
>>
>> How ROOT can help me in this double task: 1) perform the interpolation
>> to find the (x,y) that Chi2(x,y) = 10.64 and 2) plot the result?
>>
>> Regards
>> J.E Campagne
>>
>> ........................................................................
>> ... .LAL - IN2P3 - CNRS
>> .LAL - B.P 34 - 91898 Orsay Cedex - France
>> .Piece 108
>> .Tel +33 (0)1 64 46 84 29
>> .Fax +33 (0)1 64 46 83 97
>> ........................................................................
>> ...
>>
>>
>
> --
> Dr. Otto Schaile Department f"ur Physik, LMU M"unchen
> Phone: +49 89 289 14070 Am Coulombwall 1, D-85748 Garching, Germany
> Mobil: +49 160 1553598
> FAX: +49 89 289 14072 EMail: Otto.Schaile_at_Physik.Uni-Muenchen.DE

```...........................................................................
.LAL - IN2P3 - CNRS
.LAL - B.P 34 - 91898 Orsay Cedex - France
.Piece 108
.Tel +33 (0)1 64 46 84 29
```

.Fax +33 (0)1 64 46 83 97
```...........................................................................
```
Received on Tue Apr 26 2005 - 13:11:23 MEST

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