banfac banslv bint4 bintk bspldr bsplev bsplpp bsplvd bsplvn bvalue interv ppvalu

bvalue() double bvalue ( double  t[], double  a[], int  n, int  k, int  ideriv, double  x, int *  inbv, double  work[], int *  info  ) Evaluation of function or derivative value for B-spline Purpose This routine evaluates the B-representation (t[], a[], n, k) of a B-spline at x for the function value on ideriv = 0 or any of its derivatives on ideriv = 1, 2, ..., k-1. Right limiting values (right derivatives) are returned except at the right end point x = t[n] where left limiting values are computed. The spline is defined on t[k-1] <= x <= t[n]. bvalue returns a fatal error when x is outside of this interval. To compute left derivatives or left limiting values at a knot t[i], replace n by i-1 and set x = t[i], i = k to n. Returns Value of the ideriv-th derivative at x. Parameters [in] t[] Array t[lt] (lt >= n + k) Knot vector. [in] a[] Array a[la] (la >= n) B-spline coefficients. [in] n Number of B-spline coefficients. (n = sum of knot multiplicities - k) [in] k Order of B-spline. (k >= 1) [in] ideriv Order of the derivative. (0 <= ideriv <= k - 1) If ideriv = 0, returns the B-spline value. [in] x Argument x. (t[k-1] <= x <= t[n]) [in,out] inbv An initialization parameter. [in] Must be set to 1 when the first time bvalue is called. [out] Information for efficient processing after the initial call and inbv must not be changed by the user. Distinct splines require distinct inbv parameters. [out] work[] Array work[lwork] (lwork >= 3*k) Work array. [out] info = 0: Successful exit = -3: The argument n had an illegal value (n < k) = -4: The argument k had an illegal value (k < 1) = -5: The argument ideriv had an illegal value (ideriv < 0 or ideriv >= k) = -6: The argument x had an illegal value (x < t[k-1] or x > t[n]) = 1: A left limiting value cannot be obtained at t[k-1] Reference SLATEC