CSA2S - cubic spline approximation, simple entry for two-dimensional input, gridded output
CALL CSA2S (NI, XI, UI, KNOTS, NXO, ,NYO, XO, YO, UO, NWRK, WORK, IER)
- (integer,input) The number of input data points. It must be that NI .gt. 3 and, depending on the size of KNOTS below, NI may have to be larger.
- (real, input) An array containing the X - Y coordinates of the input data points. XI is dimensioned for 2 x NI. XI(1,L) is the X coordinate and XI(2,L) is the Y coordinate for the input domain for L=1,NI.
- (real, input) An array dimensioned for NI containing function values at the input XI values, that is UI(L) is the value of the input function at the coordinate (XI(1,L),XI(2,L)) for L=1,NI.
- (integer, input) The number of knots to be used in constructing the approximation spline. KNOTS is dimensioned for 2 and provides the number of knots to be used in the X and the Y directions. Both KNOTS(1) and KNOTS(2) must be at least 4. The larger the values for KNOTS, the closer the approximated curve will come to passing through the input function values.
- (integer, input) The number of X coordinate values in the output grid.
- (integer, input) The number of Y coordinate values in the output grid.
- (real, input) An array dimensioned for NXO containing the X coordinates of the output surface.
- (real, input) An array dimensioned for NYO containing the Y coordinates of the output surface.
- (real, output) An array dimensioned for NXO x NYO containing the calculated function values for the output surface. UO(I,J) is the calculated functional value at (XO(I),YO(J)) for I=1,NXO and J=1,NYO.
- (integer, input) The size of the WORK array. NWRK must be at least KNOTS(1)*KNOTS(2)*(KNOTS(1)*KNOTS(2)+3).
- (real, input) A work array dimensioned for NWRK.
- (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.
CSA2S is called to find an approximating cubic spline surface for two-dimensional input data. If you want to weight the input data values, calculate derivatives, or handle data sparse areas specially, then you will need to use CSA2XS.
To use CSA2S, load the NCAR Graphics library ngmath.
csagrid, csa2xs, csa2ls, csa2lxs
Complete documentation for Csagrid is available at URL
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University Corporation for Atmospheric Research
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