spline(1G) spline(1G)
NAME
spline- interpolate smooth curve
SYNOPSIS
spline [-a] [-k] [-n] [-p] [-x]
DESCRIPTION
spline takes pairs of numbers from the standard input as
abscissas 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., pp. 349ff) has two
continuous derivatives, and sufficiently many points to look
smooth when plotted.
The following flag options are recognized, each as a
separate argument:
-a Supply abscissas automatically (they are missing from
the input); spacing is '
g'
iven by the next argument, or
is assumed to be''
1 =
ifkn
ye
n-
x1
t argument is not a number.
is set b'
y',
the ne
yn
xt argument (default k = 0).
-k T'
hé =
cok
ns
y1
tant k used in the boundary value computation:
-n S
y0
pace output points so that approximately n intervals
occur between the lower and upper x limits (default n =
100).
-p Make output periodic, i.e., match derivatives at ends.
First and last input values should normally agree.
-x Next 1 (or 2) arguments are lower (and upper) x limits.
Normally, these limits are calculated from the data.
Automatic abscissas start at lower limit (default 0).
EXAMPLE
spline -n 10 > spline.out
0 0
1 2
2 4
3 9
will create the file spline.out with the contents:
3.000000 8.999999
2.666667 7.096296
2.333333 5.370370
2.000000 4.000000
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spline(1G) spline(1G)
1.666667 3.096296
1.333333 2.503703
1.000000 2.000000
0.666667 1.407407
0.333333 0.725926
0.000000 0.000000
FILES
/usr/bin/spline
DIAGNOSTICS
When data is not strictly monotone in x, spline reproduces
the input without interpolating extra points.
BUGS
A limit of 1,000 input points is enforced silently.
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