aspline - Akima spline interpolation

**aspline** [-a

*xstep*] [-l

*llim*] [-u

*ulim*] [-n

*n*]
{

*file(s)*}

*aspline* reads pairs of numbers from the indicated

*file(s)* (or from
stdin if no files were given) as abscissas and ordinates of a function. It
produces a similar set, which is approximately equally spaced and includes the
input set on standard output. The output is an

*Akima*-interpolated
spline which has an continuous first derivative. The second derivate may be
discontinuous, but the output does not wiggle as it would do with cubic
splines.

Datasets are separated by blank lines.

**-a ***incr*, **--auto=***incr*
- supply abscissas automatically, since they are missing from
the input; spacing is given by the next argument, or is assumed to be 1,
if next argument is not a number.

**-l ***llim*, **--llimit=***llim*
- set lower x-limit to
*llim*,

**-u ***ulim*, **--ulimit=***ulim*
- set upper x-limit to
*ulim*,

**-n ***n*, **--points=***n*
- space output points so that approx.
*n* intervals
occur between the lower and upper limit,

**-v**
- be verbose,

**-h**
- print help message on stderr and exit.

**spline**(1),

**gnuplot**(1).

*H. Akima,* *A New Method of Interpolation and Smooth Curve Fitting Based
on* *Local Procedures,* *Journal of Assc. for Comp. Mach., Vol. 17,
No. 4, Oct. 1970,* *pp. 589—602*
If you need a continuous second derivative, use

*spline* from the plotutils
package instead.