RATIONAL SPLINE SUBROUTINES

( NASA Langley Research Center )

     Scientific data often contains random errors that make plotting and
curve-fitting difficult. The Rational-Spline Approximation with Auto-
matic Tension Adjustment algorithm lead to a flexible, smooth representa-
tion of experimental data.

     The user sets the conditions for each consecutive pair of knots:(knots
are user-defined divisions in the data set) to apply no tension; to ap-
ply fixed tension; or to determine tension with a tension adjustment al-
gorithm. The user also selects the number of knots, the knot abscissas,
and the allowed maximum deviations from line segments. The selection of
these quantities depends on the actual data and on the requirements of a
particular application. This program differs from the usual spline under
tension in that it allows the user to specify different tension values be-
tween each adjacent pair of knots rather than a constant tension over the
entire data range. The subroutines use an automatic adjustment scheme that
varies the tension parameter for each interval until the maximum deviation
of the spline from the line joining the knots is less than or equal to a user-
specified amount. This procedure frees the user from the drudgery of ad-
justing individual tension parameters while still giving control over the
local behavior of the spline

     The Rational Spline program was written completely in FORTRAN for im-
plementation on a CYBER 850 operating under NOS. It has a central memory re-
quirement of approximately 1500 words. The program was released in 1988.

     COSMIC, and the COSMIC logo are registered trademarks of the National
Aeronautics and Space Administration. All other brands and product names
are the trademarks of their respective holders.



LANGUAGE: FORTRAN V

MACHINE REQUIREMENTS: CDC CYBER 170

PROGRAM SIZE: APPROXIMATELY 2,312 SOURCE STATEMENTS

DISTRIBUTION MEDIA: 9 Track 1600 BPI ASCII Card Image Format Magnetic Tape

PROGRAM NUMBER: LAR-13694

DOMESTIC - DOCUMENTATION PRICE: $16.00    PROGRAM PRICE: $800.00

INTERNATIONAL - DOCUMENTATION PRICE: $32.00   PROGRAM PRICE: $1600.00



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