chfdv chfev pchbs pchcm pchfd pchfe pchic pchim pchse pchsp

pchic() void pchic ( int  ic[], double  vc[], double  sw, int  n, double  x[], double  f[], double  d[], int  incfd, double  work[], int  lwork, int *  info  ) Piecewise cubic Hermite interpolation Purpose This routine sets derivatives needed to determine a monotone piecewise cubic Hermite interpolant. User control is available over boundary conditions and/or treatment of points where monotonicity switches direction. The resulting piecewise cubic Hermite function may be evaluated by pchfe or pchfd. Parameters [in] ic[] Array ic[lic] (lic >= 2) Specification of desired boundary conditions. ic[0] = Desired condition at beginning of data.   = 0: The default boundary condition (the same as used by pchim).   > 0: The boundary derivative is not to be adjusted for monotonicity.   < 0: The derivative is to be adjusted for monotonicity.   Allowable values for the magnitude of ic[0] are:   = 1: if first derivative at x[0] is given in vc[0]   = 2: if second derivative at x[0] is given in vc[0]   = 3: to use the 3-point difference formula for d[0] (reverts to the default boundary conditions if n < 3)   = 4: to use the 4-point difference formula for d[0] (reverts to the default boundary conditions if n < 4)   = 5: to set d[0] so that the second derivative is continuous at x[1] (reverts to the default boundary conditions if n < 4) ic[1] = Desired condition at end of data.   It may take on the same values as ic[0], but applied to derivative at x[n-1]. In the case ic[1] = 1 or 2, the value is given in vc[1]. [in] vc[] Array vc[lvc] (lvc >= 2) Specification of desired boundary values, as indicated above. vc[0] need to be set only if ic[0] = 1 or 2. vc[1] need to be set only if ic[1] = 1 or 2. [in] sw Indicates desired treatment of points where direction of monotonicity switches. = 0: Interpolant is required to be monotonic in each interval, regardless of monotonicity of data. != 0: Use a formula based on the 3-point difference formula in the vicinity of switch points. > 0: The interpolant on each interval containing an extremum is controlled to not deviate from the data by more than sw*dfloc, where dfloc is the maximum of the change of f[] on this interval and its two immediate neighbors. < 0: No such control is to be imposed. [in] n Number of data points. (n >= 2) [in] x[] Array x[lx] (lx >= n) independent variable values. The elements of x[] must be strictly increasing. [in] f[] Array f[lf] (lf >= incfd*(n - 1) + 1) Dependent variable values to be interpolated. [out] d[] Array d[ld] (ld >= incfd*(n - 1) + 1) Derivative values at the data points. [in] incfd Increment between successive values in f[] and d[]. f[i*incfd] and d[i*incfd] are the values corresponding to x[i]. (i = 0 to n - 1) [out] work[] Array work[lwork] Work array. [out] lwork The size of array work[]. (lwork >= 2*(n - 1)) [out] info = 0: Successful exit = -1: The argument ic[] had an illegal value (abs(ic[0]) > 5 and/or abs(ic[1]) > 5) = -4: The argument n had an illegal value (n < 2) = -5: The argument x[] had an illegal value (not strictly increasing) = -8: The argument incfd had an illegal value (incfd < 1) = -10: The argument lwork had an illegal value (lwork < 2*(n-1)) = 1 ic[0] < 0 and d[0] had to be adjusted for monotonicity = 2 ic[1] < 0 and d[(n-1)*incfd] had to be adjusted for monotonicity = 3: Both of the above are true Reference SLATEC (PCHIP)