spline.1g

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 1G 代码 · 共 178 行

.\" SCCSID: @(#)spline.1g	8.1	9/11/90
.\" SCCSID: @(#)spline.1g	8.1	9/11/90
.TH spline 1g 
.SH Name
spline \- interpolate smooth curve
.SH Syntax
.B spline
[\|\fIoption...\fR\|] 
.SH Description
.NXR "spline command"
.NXA "graph command" "spline command"
.NXA "plot command" "spline command"
The
.PN spline
command
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,
.\" .ft I
.\" Numerical Methods for Scientists and Engineers,
.\" .ft R
.\" 2nd ed., 349ff)
has two continuous derivatives,
and a sufficient number of points to look smooth when plotted.
.SH Options
The following options are recognized,
each as a separate argument.
.IP \fB\-a\fR 0.3i
Supplies abcissa automatically and uses specified number (next argument) for
spacing.  Default is 1.  
.IP \fB\-k\fR 0.3i
Sets the boundary constant to the specified value (next argument).  
By default
.IR k ""
= 0.
For example, 
.IP
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.ti +1.5i
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.as 11 "\*(12
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.ds 12 "\|\|
.nr 12 \w'\*(12'
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..
.if t .ig
.ce
(2nd deriv. at end) = k*(2nd deriv. next to end)
..
.IP
.br
.IP \fB\-n\fR 0.3i
Uses specified number (\fIn\fR)
in calculating intervals between lower and upper limits.  
(Default
.I n
= 100.)
.IP \fB\-p\fR 0.3i
Periodically produces output (matches derivates at ends).  
First and last input values should normally agree.
.IP \fB\-x\fR 0.3i
Uses specified numbers (next arguments) as lower and upper limits.  
Normally these limits are calculated from the data.
Automatic abcissas start at lower limit
(default 0).
.SH Restrictions
A limit of 1000 input points is enforced silently.
.SH Diagnostics
When data is not strictly monotone in
.I x,
.PN spline
reproduces the input without interpolating extra points.
.SH See Also
graph(1g), plot(1g)