WPchfe WPchia WPchse

WPchfe() Function WPchfe ( Ne As  Long, Xe As  Variant, N As  Long, X As  Variant, Y As  Variant, D As  Variant  ) Piecewise cubic Hermite (or cubic spline) function evaluator Purpose WPchfe evaluates a piecewise cubic Hermite function at an array of points. This function can be used as an evaluator for WPchse. Returns Ne+1 x 1 Column 1 Rows 1 to Ne Evaluated values of the cubic spline function Row Ne+1 Return code Return code = 0: Successful exit = i > 0: Extrapolation was performed at i points Parameters [in] Ne Number of evaluation points. (Ne >= 1) [in] Xe (Ne) Points at which the function is to be evaluated. Notes 1: The evaluation will be most efficient if the elements of Xe are increasing relative to X; that is, Xe(j) >= X(i) implies Xe(k) >= X(i), all k >= j. Note 2: If any of the Xe are outside the interval [ X(0), X(n-1) ], values are extrapolated from the nearest extreme cubic, and a return code > 0 will be returned. [in] N Number of data points (which were used by Pchse to compute coefficients). (N >= 2) [in] X (N) The data abscissas (which were used by Pchse to compute coefficients). [in] Y (N) The data ordinates (which were used by Pchse to compute coefficients). [in] D (N) An array of cubic spline coefficients computed by Pchse. Reference SLATEC (PCHIP) Example Interpolate the following natural logarithm table by WPchse. And compute ln(0.115) and ln(0.125) by WPchfe. x ln(x) ------ -------- 0.10 2.3026 0.11 2.2073 0.12 2.1203 0.13 2.0402 ------ --------