pchfe pchia pchse

pchse() def pchse ( n  , x  , f  , d  , incfd  = 1  ) Piecewise cubic spline interpolation ("not a knot" condition) Purpose pchse computes the derivatives needed to determine the Hermite representation of the cubic spline interpolant to given data, with with the default boundary conditions ("not a knot" condition). The resulting piecewise cubic spline function may be evaluated by pchfe or pchfd. Returns info (int) = 0: Successful exit = -1: The argument n had an illegal value (n < 2) = -2: The argument x is invalid (e.g. not strictly increasing) = -3: The argument f is invalid = -4: The argument d is invalid = -5: The argument incfd had an illegal value (incfd < 1) Parameters [in] n Number of data points. (n >= 2) [in] x Numpy ndarray (1-dimensional, float, length n) Independent variable values. The elements of x[] must be strictly increasing. [in] f Numpy ndarray (1-dimensional, float, length incfd*(n - 1) + 1) Dependent variable values to be interpolated. f[i*incfd] is the value corresponding to x[i] (i = 0 to n - 1). [out] d Numpy ndarray (1-dimensional, float, length incfd*(n - 1) + 1) Derivative values at the data points. These values will determine the cubic spline interpolant with the requested boundary conditions. The value corresponding to x[i] is stored in d[i*incfd] (i = 0 to n - 1). No other entries in d are changed. [in] incfd (Optional) Increment between successive values in f and d. This argument is provided primarily for 2-D applications. (incfd >= 1) (default = 1) Reference SLATEC (PCHIP) (Driver for pchsp) Example Program Compute ln(0.115) and ln(0.125) by interpolating the following natural logarithm table with cubic spline. x ln(x) ------ --------- 0.10 -2.3026 0.11 -2.2073 0.12 -2.1203 0.13 -2.0402 ------ --------- def TestPchse(): n = 4 x = np.array([0.1, 0.11, 0.12, 0.13]) y = np.array([-2.3026, -2.2073, -2.1203, -2.0402]) d = np.empty(n) info = pchse(n, x, y, d) print(info) if info == 0: ne = 2 xe = np.array([0.115, 0.125]) ye = np.empty(ne) info = pchfe(n, x, y, d, ne, xe, ye) print(ye, info) Example Results >>> TestPchse() 0 [-2.16285 -2.079475] 0