Datafitting - Cubic Spline Boundary Conditions

Page__Chris — Sat, 16 Nov 2019 12:02:42 GMT

I would like to fit a cubic spline with the second derivatives at the end points linearly extrapolated from the two closest interior points. Is there a way to specify this type of boundary condition?

Hi Chris,

Pavel_D_Intel1 — Wed, 20 Nov 2019 08:19:22 GMT

Hi Chris,

Intel MKL Data Fitting supports next types of boundary conditions for cubic splines:

not-a-knot
free end
periodic
user-definedе the first/second derivative at the left/right endpoint

You can set the specifically defined second derivatives at the endpoints as presented below:

…
MKL_INT bc_type; // boundary conditions type
double bc[2]; // array of boundary conditions
…
bc_type = DF_BC_2ND_LEFT_DER | DF_BC_2ND_RIGHT_DER;
bc[0] = a;
bc[1] = b;
…
// Call dfdEditPPSpline1D( task, sorder, stype, bc_type, bc, ic_type, ic, scoeff, scoeffhint );
// Call dfdConstruct1D( task, DF_PP_SPLINE, DF_METHOD_STD );

Full code can be found in “dfdcubicsplineint2der.c” sample.

Feel free to ask more.

Best regards,
Pavel.

topic Datafitting - Cubic Spline Boundary Conditions in Intel® oneAPI Math Kernel Library

Datafitting - Cubic Spline Boundary Conditions

Hi Chris,