Dear all,
I'm using the GSL B-spline functions to implement cubic spline
smoothing. My program is based on the example in the manual
(http://www.gnu.org/software/gsl/manual/html_node/Example-programs-for-B_002dsplines.html).
I want to allow varying numbers of breakpoints (nbreak) to achieve
different degrees of smoothing. The minimum nbreak for cubic splines is
2, but is there a maximum? If I use more than n-2 (where n is the number
of data points), I get an error from "gsl_multifit_wlinear" when
computing the spline coefficients:
gsl: svd.c:236: ERROR: svd of MxN matrix, M<N, is not implemented
For the offending fit matrix, M = n and N = ncoeffs = nbreak+k-2 = nbreak+2.
Is there a way to use every (distinct location of a) data point as a
breakpoint (via "gsl_bspline_knots")?
Would it be possible to have more breakpoints than data points? If so,
would it make any sense to allow this?
Best regards
Hendrik
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