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########################################################################
##
## Copyright (C) 2007-2025 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## This file is part of Octave.
##
## Octave 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 3 of the License, or
## (at your option) any later version.
##
## Octave 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.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING. If not, see
## <https://www.gnu.org/licenses/>.
##
########################################################################
## -*- texinfo -*-
## @deftypefn {} {} slice (@var{x}, @var{y}, @var{z}, @var{v}, @var{sx}, @var{sy}, @var{sz})
## @deftypefnx {} {} slice (@var{x}, @var{y}, @var{z}, @var{v}, @var{xi}, @var{yi}, @var{zi})
## @deftypefnx {} {} slice (@var{v}, @var{sx}, @var{sy}, @var{sz})
## @deftypefnx {} {} slice (@var{v}, @var{xi}, @var{yi}, @var{zi})
## @deftypefnx {} {} slice (@dots{}, @var{method})
## @deftypefnx {} {} slice (@var{hax}, @dots{})
## @deftypefnx {} {@var{h} =} slice (@dots{})
## Plot slices of 3-D data/scalar fields.
##
## Each element of the 3-dimensional array @var{v} represents a scalar value at
## a location given by the parameters @var{x}, @var{y}, and @var{z}. The
## parameters @var{x}, @var{y}, and @var{z} are either 3-dimensional arrays of
## the same size as the array @var{v} in the @qcode{"meshgrid"} format or
## vectors. The parameters @var{xi}, etc.@: respect a similar format to
## @var{x}, etc., and they represent the points at which the array @var{vi}
## is interpolated using interp3. The vectors @var{sx}, @var{sy}, and
## @var{sz} contain points of orthogonal slices of the respective axes.
##
## If @var{x}, @var{y}, @var{z} are omitted, they are assumed to be
## @code{x = 1:size (@var{v}, 2)}, @code{y = 1:size (@var{v}, 1)} and
## @code{z = 1:size (@var{v}, 3)}.
##
## @var{method} is one of:
##
## @table @asis
## @item @qcode{"nearest"}
## Return the nearest neighbor.
##
## @item @qcode{"linear"}
## Linear interpolation from nearest neighbors.
##
## @item @qcode{"cubic"}
## Cubic interpolation from four nearest neighbors (not implemented yet).
##
## @item @qcode{"spline"}
## Cubic spline interpolation---smooth first and second derivatives
## throughout the curve.
## @end table
##
## The default method is @qcode{"linear"}.
##
## If the first argument @var{hax} is an axes handle, then plot into this axes,
## rather than the current axes returned by @code{gca}.
##
## The optional return value @var{h} is a graphics handle to the created
## surface object.
##
## Examples:
##
## @example
## @group
## [x, y, z] = meshgrid (linspace (-8, 8, 32));
## v = sin (sqrt (x.^2 + y.^2 + z.^2)) ./ (sqrt (x.^2 + y.^2 + z.^2));
## slice (x, y, z, v, [], 0, []);
##
## [xi, yi] = meshgrid (linspace (-7, 7));
## zi = xi + yi;
## slice (x, y, z, v, xi, yi, zi);
## @end group
## @end example
## @seealso{interp3, surface, pcolor}
## @end deftypefn
function h = slice (varargin)
[hax, varargin, nargs] = __plt_get_axis_arg__ ("slice", varargin{:});
method = "linear";
if (ischar (varargin{end}))
method = varargin{end};
nargs -= 1;
endif
if (nargs == 4)
v = varargin{1};
if (ndims (v) != 3)
error ("slice: V must be a 3-dimensional array of values");
endif
[nx, ny, nz] = size (v);
[x, y, z] = meshgrid (1:nx, 1:ny, 1:nz);
sx = varargin{2};
sy = varargin{3};
sz = varargin{4};
elseif (nargs == 7)
v = varargin{4};
if (ndims (v) != 3)
error ("slice: V must be a 3-dimensional array of values");
endif
x = varargin{1};
y = varargin{2};
z = varargin{3};
if (isvector (x) && isvector (y) && isvector (z))
[x, y, z] = meshgrid (x, y, z);
elseif (ndims (x) == 3 && size_equal (x, y, z))
## Do nothing.
else
error ("slice: X, Y, Z size mismatch");
endif
sx = varargin{5};
sy = varargin{6};
sz = varargin{7};
else
print_usage ();
endif
if (any ([isvector(sx), isvector(sy), isvector(sz)]))
have_sval = true;
elseif (ndims (sx) == 2 && size_equal (sx, sy, sz))
have_sval = false;
else
error ("slice: dimensional mismatch for (XI, YI, ZI) or (SX, SY, SZ)");
endif
oldfig = [];
if (! isempty (hax))
oldfig = get (0, "currentfigure");
endif
unwind_protect
hax = newplot (hax);
sidx = 1;
minv = min (v(:));
maxv = max (v(:));
set (hax, "clim", double ([minv, maxv]));
if (have_sval)
ns = length (sx) + length (sy) + length (sz);
hs = zeros (ns,1);
[ny, nx, nz] = size (v);
if (length (sz) > 0)
for i = 1:length (sz)
[xi, yi, zi] = meshgrid (squeeze (x(1,:,1)),
squeeze (y(:,1,1)), sz(i));
vz = squeeze (interp3 (x, y, z, v, xi, yi, zi, method));
htmp(sidx++) = surface (xi, yi, sz(i) * ones (size (yi)), vz);
endfor
endif
if (length (sy) > 0)
for i = length (sy):-1:1
[xi, yi, zi] = meshgrid (squeeze (x(1,:,1)),
sy(i),
squeeze (z(1,1,:)));
vy = squeeze (interp3 (x, y, z, v, xi, yi, zi, method));
htmp(sidx++) = surface (squeeze (xi),
squeeze (sy(i) * ones (size (zi))),
squeeze (zi), vy);
endfor
endif
if (length (sx) > 0)
for i = length (sx):-1:1
[xi, yi, zi] = meshgrid (sx(i), squeeze (y(:,1,1)), squeeze (z(1,1,:)));
vx = squeeze (interp3 (x, y, z, v, xi, yi, zi, method));
htmp(sidx++) = surface (squeeze (sx(i) * ones (size (zi))),
squeeze (yi), squeeze (zi), vx);
endfor
endif
else
vi = interp3 (x, y, z, v, sx, sy, sz);
htmp = surface (sx, sy, sz, vi);
endif
if (! ishold ())
set (hax, "view", [-37.5, 30.0],
"xgrid", "on", "ygrid", "on", "zgrid", "on");
endif
unwind_protect_cleanup
if (! isempty (oldfig))
set (0, "currentfigure", oldfig);
endif
end_unwind_protect
if (nargout > 0)
h = htmp;
endif
endfunction
%!demo
%! clf;
%! colormap ("default");
%! [x, y, z] = meshgrid (linspace (-8, 8, 32));
%! v = sin (sqrt (x.^2 + y.^2 + z.^2)) ./ (sqrt (x.^2 + y.^2 + z.^2));
%! slice (x, y, z, v, [], 0, []);
%! title ("slice() demo #1");
%!demo
%! clf;
%! colormap ("default");
%! [x, y, z] = meshgrid (linspace (-8, 8, 32));
%! v = sin (sqrt (x.^2 + y.^2 + z.^2)) ./ (sqrt (x.^2 + y.^2 + z.^2));
%! [xi, yi] = meshgrid (linspace (-7, 7));
%! zi = xi + yi;
%! slice (x, y, z, v, xi, yi, zi);
%! title ("slice() demo #2");
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