csa1xs calculates an approximating cubic spline for one-dimensional input data. c_csa1xs 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 c_csa1s.
Note: This function is only available in version 4.1.1 of NCL. If your site is licensed for version 4.1, then you can get version 4.1.1 for free. To get version 4.1.1 of NCAR Graphics software, please contact your site representative. If you don't know who your site representative is, then send email to ncarginf@ucar.edu or call (303) 497-1201.
function csa1xs( xi[*] : float, yi[*] : float, wts[*] : float, knots[1] : integer smth[1] : float nderiv[1] : float xo[*] : float )
csa1xs is in the csagrid package - a software package in the ngmath library that implements a cubic spline approximation algorithm to fit a function to input data. The input for the approximation is a set of randomly-spaced data. These data may be one-dimensional, two-dimensional, or three-dimensional.
The general documentation for csagrid contains several complete examples for entries in the csagrid package.
begin ;----------- Define original data -------------------------------------- xi = (/0.0, 0.1, 0.2, 0.3, 0.5, 0.6, 0.65, 0.8, 0.9, 1./) yi = (/0.0, 0.8, -0.9, -0.9, 0.9, 1.0, 0.90, -0.8, -0.8, 0./) npts = 101 xo = fspan(0.0,1.0,npts) ; Create the output X coordinate array. ;--- Calculate approximated first derivative values. knots = 4 wts = -1. smth = 0. nderiv = 1 yo = csa1xs(xi,yi,wts,knots,smth,nderiv,xo) end
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