R help - Apr 2009 - DierckxSpline fitting with different sets of y-values in one time

Dear "R" users,

I have a question about the Package DierckxSpline. I have tried to find the
answer by myself but it didn't worked out.

I wondered if Dierckxspline can use different sets of y values in one time to
fit a line with knot. I have different sets of Y values representing the same
thing for different voxels (in an fmri image). I have already fitted the data in
different graphs and I know now that the plots are comparable for the different
data sets (so for the different voxels) but I wanted to include all the
information in one plot, If it's possible. So I want to know the best
fitting line for the whole cluster of voxels except for one voxel.
If there is no possibility to do this I tought it would be an option to take the
mean of the different y-values and use those values but I don't know if this
is mathematical right to do.
I hope someone can help me with this.

Thank you very much,
Elisabeth Jonckers
GIfMI
Ghent University Hospital
Belgium

	[[alternative HTML version deleted]]

Dear Elisabeth: 

      Have you tried it?  I have not, but I suspect the answer is
"no".

      What problem are you trying to solve?  You might get more useful 
suggestions from this list if you provide commented, minimal, 
self-contained, reproducible code describing your problem and what 
you've tried to solve it, as suggested in the posting guide 
"www.R-project.org/posting-guide.html". 

      With fmri images, I might look first at the "fields" package, 
because it is explicitly designed for "curve, surface and function 
fitting with an emphasis on splines, spatial data and spatial 
statistics. The major methods include cubic, robust, and thin plate 
splines, multivariate Kriging and Kriging for large data sets."  I have 
not used it, but it sounds to me like you might want thin plate 
splines.  Paul Dierckx (1993) Curve and Surface Fitting with Splines 
(Oxford Science Publications) discusses thin plate splines, and Dierckx 
wrote Fortran to fit them.  However, the "DierckxSpline" package does 
not currently connect to those capabilities. 

      If univariate splines would do, I might start with the "fda" 
package.  The theory behind that is documented in two books by Ramsay 
and Silverman. 

      Hope this helps. 
      Spencer Graves

Jonckers Elisabeth wrote:
> Dear "R" users,
>
> I have a question about the Package DierckxSpline. I have tried to find the
answer by myself but it didn't worked out.
>
> I wondered if Dierckxspline can use different sets of y values in one time
to fit a line with knot. I have different sets of Y values representing the same
thing for different voxels (in an fmri image). I have already fitted the data in
different graphs and I know now that the plots are comparable for the different
data sets (so for the different voxels) but I wanted to include all the
information in one plot, If it's possible. So I want to know the best
fitting line for the whole cluster of voxels except for one voxel.
> If there is no possibility to do this I tought it would be an option to
take the mean of the different y-values and use those values but I don't
know if this is mathematical right to do.
> I hope someone can help me with this.
>
> Thank you very much,
> Elisabeth Jonckers
> GIfMI
> Ghent University Hospital
> Belgium
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>