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

interv() void interv ( double  xt[], int  lxt, double  x, int *  ilo, int *  ileft, int *  info  ) 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] 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 = -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