NAME

spline − interpolate smooth curve

SYNOPSIS

spline [ option ] ... 

DESCRIPTION

Spline takes pairs of numbers from the standard input as abcissas and ordinates of a function.  It produces a similar set, which is approximately equally spaced and includes the input set, on the standard output.  The cubic spline output (R. W. Hamming, Numerical Methods for Scientists and Engineers, 2nd ed., 349ff) has two continuous derivatives, and sufficiently many points to look smooth when plotted, for example by plot (I).  The following options are recognized, each as a separate argument.

aSupply abscissas automatically (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. 

kThe constant k used in the boundary value computation

y′′0=ky′′1,y′′n=ky′′n−1is set by the next argument. By default k = 0. 

nSpace output points so that approximately n points occur between the lower and upper x limits.  (Default n = 100.) 

pMake output periodic, i.e. match derivatives at ends.  First and last input values should normally agree. 

xNext 1 (or 2) arguments are lower (and upper) x limits.  Normally these limits are calculated from the data.  Automatic abcissas start at lower limit (default 0). 

SEE ALSO

plot (I)

AUTHOR

M. D. McIlroy

BUGS

A limit of 1000 input points is enforced silently.