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## Copyright (C) 2003 Joao Cardoso.
##
## This program is free software; you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2, or (at your option)
## any later version.
##
## This program is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
## General Public License for more details.
##
## This file is part of plplot_octave.
## usage: zg = griddata(x, y, z, xg, yg [,method [, arg]])
##
## griddata takes irregularly sampled data from three input arrays
## x[npts], y[npts], and z[npts], reads the desired grid location from
## input arrays xg[nptsx] and yg[nptsy], and returns the gridded data
## into output array zg[nptsx][nptsy].
##
## The algorithm used to grid the data is specified with the argument
## method. The algorithm can use argument arg.
## The available(*) algorithms are:
##
## GRID_CSA: Bivariate Cubic Spline approximation
## GRID_DTLI: Delaunay Triangulation Linear Interpolation
## GRID_NNI: Natural Neighbors Interpolation
## GRID_NNIDW: Nearest Neighbors Inverse Distance Weighted
## GRID_NNLI: Nearest Neighbors Linear Interpolation
## GRID_NNAIDW: Nearest Neighbors Around Inverse Distance Weighted (default)
##
## Some algorithms can generate NaNs, and as PLplot is not NaN aware the
## returned data must be treated before being plotted, e.g., zg(isnan (zg)) = 0;
##
## (*) Some algorithms might not be present in your system, depending
## on the availability of the QHull library.
## GRID_CSA, GRID_DTLI and GRID_NNI use the csa and nn library from
## Pavel Sakof, http://www.marine.csiro.au/~sakov/
function zg = griddata(x, y, z, xg, yg, method, arg)
__pl_init;
global GRID_CSA GRID_DTLI GRID_NNI GRID_NNIDW GRID_NNLI GRID_NNAIDW
if (nargin < 5)
help griddata
return;
endif
if (is_vector(x) && is_vector(y) && is_vector(z) &&
is_vector(xg) && is_vector(yg))
[err, x, y, z] = common_size(x, y, z);
if (err)
help griddata
return;
endif
if (nargin == 5)
method = GRID_NNAIDW;
arg = 15;
elseif (nargin == 6)
arg = 0;
endif
if (! any(method == [GRID_CSA GRID_DTLI GRID_NNI GRID_NNIDW GRID_NNLI GRID_NNAIDW]))
help griddata
return
endif
if (rows(xg) == 1)
xg = xg';
endif
if (rows(yg) == 1)
yg = yg';
endif
zg = plgriddata(x, y, z, xg, yg, method, arg);
##if (any(any(isnan(zg))))
## warning("griddata: NaNs returned.");
##endif
else
help griddata
return
endif
endfunction
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