Banfac Banslv Bint4 Bintk Bspldr Bsplev Bsplpp Bsplvd Bsplvn Bvalue Interv Ppvalu

Interv() Sub Interv ( Xt() As  Double, Lxt As  Long, X As  Double, Ilo As  Long, Ileft As  Long, Info As  Long  ) Compute Ileft for the input to Bsplvd and Bsplvn Purpose This routine computes the largest integer Ileft in 1 <= Ileft <= Lxt such that Xt(Ileft-1) <= X where Xt() is a subdivision of the X interval. Precisely, the following values will be returned.   If X < Xt(0) then Ileft = 1, Info = 2   If Xt(i-1] <= X < Xt(i) then Ileft = i, Info = 0   If Xt(Lxt-1] <= X then Ileft = Lxt, Info = 1 When multiplicities are present in the break point to the left of X, the largest index is taken for Ileft. Parameters [in] Xt() Array Xt(LXt - 1) Knot or break point vector. [in] Lxt Length of the vector Xt(). (Lxt >= 1) [in] X Argument X. [in,out] Ilo Initialization parameter. [in] Must be set to 1 the first time the array Xt() is processed by Interv. [out] Information for efficient processing after the initial call and Ilo must not be changed by the user. Distinct splines require distinct Ilo parameters. [out] Ileft Largest integer satisfying Xt(Ileft-1) <= X. [out] Info = 0: Successful exit. = -1: The argument Xt() is invalid. = -2: The argument Lxt had an illegal value. (Lxt < 1) = 1: X lies out of bounds. (Xt(Lxt-1) <= X) = 2: X lies out of bounds. (X < Xt(0)) Reference SLATEC Example Program See example of Bsplvn and Bsplvd.