CSA3LXS(3NCARG)

✨ CSA3LXS — cubic spline approximation, the expanded entry for 3-D input with list output ✨

okay so bestie, welcome to CSA3LXS 💖 this is one of those NCAR Graphics joints (section 3NCARG, she's fancy), and she's the expanded version of the 3-D cubic spline approximation routine — the one you call when you want list output and you're feeling a little extra. 🎀

🌸 SYNOPSIS 🌸

CALL CSA3LXS (NI, XI, UI, WTS, KNOTS, SMTH, NDERIV,
              NO, XO, YO, ZO, UO, NWRK, WORK, IER)

💅 DESCRIPTION 💅

okay here's the whole cast, one by one, no skips:

• NI (integer, input) — the number of input data points. it's gotta be that NI .gt. 3 and, depending on how big KNOTS is (see below 👇), NI might have to be even bigger than that. the math is mathing, she has needs.
• XI (real, input) — an array holding the X-Y-Z coordinates of your 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. (yeah girl, it says XI(2,L) both times — that's literally what the page says, i'm just the messenger 🙈)
• UI (real, input) — an array dimensioned for NI holding the 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. she's giving "the actual data" energy 💜
• 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 do not want to weight your input UI values, just set WTS(1) to -1 and call it a day ✨ the weights in WTS are relative and can be any non-negative value. when CSA3LXS is called, the weights get summed and each individual weight gets normalized so the weight sum is unity. iconique. 💅
• KNOTS (integer, input) — how many knots you want used when constructing the approximation spline. KNOTS is dimensioned for 3 and hands you the number of knots for the X, Y, and Z directions. KNOTS(I) must be at least 4 for I=1,3. the bigger your KNOTS values, the closer the approximated curve comes to passing through the input function values. more knots = more clingy, lowkey 🫶
• SMTH (real, input) — a parameter that controls extrapolation into data sparse regions. if SMTH is zero, then nothing special happens in those sparse regions. a good first choice for SMTH is 1. start there bestie, trust. 🌈
• NDERIV (integer, input) — an array dimensioned for 3 that tells you, for each coordinate, whether you want functional values (=0), first derivative values (=1), or second derivative values (=2). pick your fighter. ⭐
• NO (integer, input) — the number of coordinate values in the output list. NO can be any positive number. any. positive. number. periodt. 👑
• XO (real, input) — an array dimensioned for NO holding the X coordinates of the output list.
• YO (real, input) — an array dimensioned for NO holding the Y coordinates of the output list.
• ZO (real, input) — an array dimensioned for NO holding the Z coordinates of the output list.
• UO (real, output) — an array dimensioned for NO holding the calculated function values for the output spline. UO(I) is the calculated functional value at (XO(I),YO(I),ZO(I)) for I=1,NO. this is the payoff, the main character moment 🔥
• 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 skip the math 🧚
• WORK (real, input) — a work array dimensioned for NWRK. she's just there to hold stuff, no thoughts head empty 💀
• IER (integer, output) — an error return value. if IER comes back as 0, then no errors were detected. if IER is non-zero, then go refer to the man page for csagrid_errors for the details. don't panic, just read. 📖

🦋 USAGE 🦋

you call CSA3LXS if you want to weight the input data values, calculate derivatives, or handle data sparse areas specially. if you don't wanna do any of those three things, then use CSA3LS instead. simple as that, bestie 💖

🎀 ACCESS 🎀

to use CSA3LXS, load the NCAR Graphics library ngmath. that's the vibe check, and she passed. ✅

🌟 SEE ALSO 🌟

• csagrid
• csa3s
• csa3xs
• csa3ls

complete documentation for Csagrid is available at URL http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html — go read it, it's giving thorough 🦋

💜 COPYRIGHT 💜

Copyright (C) 2000 University Corporation for Atmospheric Research

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

and that's the whole page, no crumbs left 🍓 this was the UNIX version, January 1999, filed under CSA3LXS(3NCARG) — mwah, take care of her, she's iconic 💅✨🎀