CSA3XS(3NCARG)

💖 CSA3XS — cubic spline approximation, the expanded entry for three-dimensional input 💖

okay so bestie, listen. this is a page from NCAR GRAPHICS, and it's the fancy deluxe version of the 3D spline approximator. it's giving "main character energy" for gridded data. let's get into it 🦋

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✨ NAME ✨

CSA3XS — cubic spline approximation, expanded entry for three-dimensional input. yeah. the expanded one. she does more than her little sister, iykyk 💅

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✨ SYNOPSIS ✨

CALL CSA3XS (NI, XI, UI, WTS, KNOTS, SMTH, NDERIV,
             NXO, ,NYO, NZO, XO, YO, ZO, UO, NWRK,
             WORK, IER)

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✨ DESCRIPTION ✨

okay so here's the whole cast of characters, one by one, no skips, no skimming, periodt 👑

• NI — (integer, input) the number of input data points. it has to be that NI .gt. 3 and, depending on how big KNOTS is (see below), NI might have to be even larger. so like, don't skimp 🍓
• XI — (real, input) an array holding the X - Y - Z coordinates of the input data points. XI is dimensioned for 3 x NI. XI(1,L) is the X coordinate, XI(2,L) is the Y coordinate, and XI(2,L) is the Z coordinate for the input domain, for L=1,NI. (yes, the original really says XI(2,L) twice — i'm not gonna gaslight you and pretend otherwise 🙈)
• UI — (real, input) an array dimensioned for NI holding function values at the input XI values, that is, UI(L) is the value of the input function at XI(L) for L=1,NI. through the input function values. ✨
• WTS — (real, input) an array dimensioned for NI holding weights for the UI values at the input XI values, that is, WTS(L) is a weight for the value of UI(L) for L=1,NI. if you don't wanna weight the input UI values, then set WTS(1) to -1. the weights in the WTS array are relative and may be set to any non-negative value. when CSA3XS is called, the weights get summed and the individual weights get normalized so that the weight sum is unity. math! slay! 💅
• KNOTS — (integer, input) the number of knots to be used in constructing the approximation spline. KNOTS is dimensioned for 3 and provides the number of knots to be used in the X, Y, and Z directions. both KNOTS(I) must be at least 4 for I=1,3. the larger the values for KNOTS, the closer the approximated curve will come to passing through the input function values. more knots = more clinging, fr fr 🎀
• SMTH — (real, input) a parameter that controls extrapolation into data sparse regions. if SMTH is zero, then nothing special is done in data sparse regions. a good first choice for SMTH is 1. (yes, 1. just trust her.) 🌸
• NDERIV — (integer, input) an array dimensioned for 3 that specifies, for each coordinate, whether you want functional values (=0), first derivative values (=1), or second derivative values (=2). pick your fighter 😤
• NXO — (integer, input) the number of X coordinate values in the output grid.
• NYO — (integer, input) the number of Y coordinate values in the output grid.
• NZO — (integer, input) the number of Z coordinate values in the output grid.
• XO — (real, input) an array dimensioned for NXO containing the X coordinates of the output spline.
• YO — (real, input) an array dimensioned for NYO containing the Y coordinates of the output spline.
• ZO — (real, input) an array dimensioned for NZO containing the Z coordinates of the output spline.
• UO — (real, output) an array dimensioned for NXO x NYO x NZO containing the calculated function values for the output function. UO(I,J,K) is the calculated functional value at (XO(I), YO(J), ZO(K)) for I=1,NXO and J=1,NYO and K=1,NZO. this is the one you came for 💖
• NWRK — (integer, input) the size of the WORK array. NWRK must be at least NK * (NK+3) where NK = KNOTS(1) * KNOTS(2) * KNOTS(3). do the math, don't be brave 💀
• WORK — (real, input) a work array dimensioned for NWRK.
• IER — (integer, output) an error return value. if IER is returned as 0, then no errors were detected. if IER is non-zero, then refer to the man page for csagrid_errors for details. 👀

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✨ USAGE ✨

CSA3XS is called to find an approximating cubic spline for three-dimensional input data. CSA3XS is called if you want to weight the input data values, calculate derivatives, or handle data sparse areas specially.

if you do not want to do any of these three things, then use CSA3S. (she's the low-key sister. still iconic, just less extra.) ✨

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✨ ACCESS ✨

to use CSA3XS, load the NCAR Graphics library ngmath. that's the whole vibe check 🧚

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✨ SEE ALSO ✨

• csagrid
• csa3s
• csa3ls
• csa3lxs

complete documentation for Csagrid is available at URL

http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html

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✨ COPYRIGHT ✨

Copyright (C) 2000 University Corporation for Atmospheric Research

The use of this Software is governed by a License Agreement.

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and that's the whole page, bestie 🫶 this came out of the UNIX manual, January 1999 vintage, filed under CSA3XS(3NCARG) — old-school but still serving looks. go forth and spline responsibly 💜✨