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## Copyright (C) 2007-2026 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
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## -*- texinfo -*-
## @deftypefn  {} {} meshz (@var{x}, @var{y}, @var{z})
## @deftypefnx {} {} meshz (@var{z})
## @deftypefnx {} {} meshz (@dots{}, @var{c})
## @deftypefnx {} {} meshz (@dots{}, @var{prop}, @var{val}, @dots{})
## @deftypefnx {} {} meshz (@var{hax}, @dots{})
## @deftypefnx {} {@var{h} =} meshz (@dots{})
## Plot a 3-D wireframe mesh with a surrounding curtain.
##
## The wireframe mesh is plotted using rectangles.  The vertices of the
## rectangles [@var{x}, @var{y}] are typically the output of @code{meshgrid}.
## over a 2-D rectangular region in the x-y plane.  @var{z} determines the
## height above the plane of each vertex.  If only a single @var{z} matrix is
## given, then it is plotted over the meshgrid
## @code{@var{x} = 1:columns (@var{z}), @var{y} = 1:rows (@var{z})}.
## Thus, columns of @var{z} correspond to different @var{x} values and rows
## of @var{z} correspond to different @var{y} values.
##
## The color of the mesh is computed by linearly scaling the @var{z} values
## to fit the range of the current colormap.  Use @code{clim} and/or
## change the colormap to control the appearance.
##
## Optionally the color of the mesh can be specified independently of @var{z}
## by supplying a color matrix, @var{c}.
##
## Any property/value pairs are passed directly to the underlying surface
## object.  The full list of properties is documented at
## @ref{Surface Properties}.
##
## 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.
##
## @seealso{mesh, meshc, contour, surf, surface, waterfall, meshgrid, hidden,
## shading, colormap, clim}
## @end deftypefn

function h = meshz (varargin)

  if (! all (cellfun ("isreal", varargin)))
    error ("meshz: X, Y, Z, C arguments must be real");
  endif

  [hax, varargin, nargin] = __plt_get_axis_arg__ ("meshz", varargin{:});

  ## Find where property/value pairs start
  charidx = find (cellfun ("isclass", varargin, "char"), 1);

  if (isempty (charidx))
    charidx = nargin + 1;
  endif

  if (nargin == 1)
    z = varargin{1};
    [m, n] = size (z);
    x = 1:n;
    y = (1:m).';
    c = z;
  elseif (nargin == 2)
    z = varargin{1};
    [m, n] = size (z);
    x = 1:n;
    y = (1:m).';
    c = varargin{2};
  elseif (charidx == 4)
    x = varargin{1};
    y = varargin{2};
    z = varargin{3};
    c = z;
  else
    x = varargin{1};
    y = varargin{2};
    z = varargin{3};
    c = varargin{4};
  endif

  ## Create a border of one rectangle (2 points) as the curtain around
  ## the data and draw it with the mean (max + min / 2) color of the data.

  if (isvector (x) && isvector (y))
    x = [x(1), x(1), x(:).', x(end), x(end)];
    y = [y(1); y(1); y(:); y(end); y(end)];
  else
    x = [x(1,1), x(1,1), x(1,:), x(1,end), x(1,end);
         x(1,1), x(1,1), x(1,:), x(1,end), x(1,end);
         x(:,1), x(:,1), x, x(:,end), x(:,end);
         x(end,1), x(end,1), x(end,:), x(end,end), x(end,end);
         x(end,1), x(end,1), x(end,:), x(end,end), x(end,end) ];
    y = [y(1,1), y(1,1), y(1,:), y(1,end), y(1,end);
         y(1,1), y(1,1), y(1,:), y(1,end), y(1,end);
         y(:,1), y(:,1), y, y(:,end), y(:,end);
         y(end,1), y(end,1), y(end,:), y(end,end), y(end,end);
         y(end,1), y(end,1), y(end,:), y(end,end), y(end,end) ];
  endif

  zref = min (z(isfinite (z)));
  z = [zref .* ones(1, columns(z) + 4);
       zref .* ones(1, 2), z(1,:), zref .* ones(1, 2);
       zref .* ones(rows(z), 1), z(:,1),z, z(:,end), zref .* ones(rows(z), 1);
       zref .* ones(1, 2), z(end,:), zref .* ones(1, 2);
       zref .* ones(1, columns(z) + 4)];

  cdat = c(isfinite (c(:)));
  cref = (min (cdat) + max (cdat)) / 2;
  c = [cref .* ones(2, columns(c) + 4);
       cref .* ones(rows(c), 2), c, cref .* ones(rows(c), 2);
       cref .* ones(2, columns(c) + 4)];

  hax = newplot (hax);
  htmp = mesh (hax, x, y, z, c, varargin{charidx:end});

  if (nargout > 0)
    h = htmp;
  endif

endfunction


%!demo
%! clf;
%! colormap ("default");
%! Z = peaks ();
%! meshz (Z);
%! title ("meshz() plot of peaks() function");

%!demo
%! clf;
%! colormap ("default");
%! Z = peaks ();
%! subplot (1,2,1)
%!  mesh (Z);
%!  daspect ([2.5, 2.5, 1]);
%!  title ("mesh() plot");
%! subplot (1,2,2)
%!  meshz (Z);
%!  daspect ([2.5, 2.5, 1]);
%!  title ("meshz() plot");

%!demo
%! clf;
%! colormap ("default");
%! [X,Y,Z] = peaks ();
%! [fx, fy] = gradient (Z);
%! C = sqrt (fx.^2 + fy.^2);
%! meshz (X,Y,Z,C);
%! title ("meshz() plot with color determined by gradient");
