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
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