Intel® oneAPI Math Kernel Library
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DataFitting question

Beginner
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Hi, In MKL documentaion (http://software.intel.com/sites/products/documentation/hpc/mkl/mklman/GUID-78250DC6-6203-42B5-B46E-638CE1BC5D88.htm#TBL17-8), 'Boundary Conditions Supported by Data Fitting Functions' says 'DF_BC_1ST_LEFT_DER' is 'The first derivative at the left endpoint is zero.'. Then what does this 'is zero' mean ?
I actually tried  NATURAL spline with DF_BC_1ST_LEFT_DER|DF_BC_1ST_RIGHT_DER options(etc),and got different results for non zero boundary values.

I also tried LINEAR spline with/without PERIODIC option, and it showed no difference even in the region outside of specified x-range.
# I got these results from 'Math Kernel Library Version 10.3.11 Product Build 20120606 for 32-bit applications' on Windows 7.

6 Replies
Black Belt
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'The first derivative at the left endpoint is zero.' This implies that you want the slope of the curve to be zero at the left endpoint,.i.e., the curve has as tangent a line with y'(x=the left endpoint) = 0. A "natural" spline is one which has no bending moment applied at the ends, i.e., y'' = 0 at those points.
Beginner
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No..., DF_BC_1ST_LEFT_DER(==bc_type) with non-zero boundary value(==bc[0]) gives you non-zero slope of the curve. > A "natural" spline is one which has no bending moment applied at the ends, i.e., y'' = 0 at those points. Yes,but MKL implementation seems to be different (Pls see DF_PP_NATURAL and DF_BC_FREE_END).
Employee
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