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+## Copyright (C) 1996 John W. Eaton
+##
+## 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 2, 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, write to the Free
+## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+## 02110-1301, USA.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} plot (@var{args})
+##
+## This function produces three-dimensional plots.  Many different
+## combinations of arguments are possible.  The simplest form is
+##
+## @example
+## plot3 (@var{x}, @var{y}, @var{z})
+## @end example
+##
+## @noindent
+## where the arguments are taken to be the vertices of the points to be
+## plotted in three dimensions. If all arguments are vectors of the same
+## length, then a single continuous line is drawn. If all arguments are
+## matrices, then each column of the matrices is treated as a seperate
+## line. No attempt is made to transpose the arguments to make the
+## number of rows match.
+##
+## To save a plot, in one of several image formats such as PostScript
+## or PNG, use the @code{print} command.
+##
+## An optional format argument can be given as
+##
+## @example
+## plot3 (@var{x}, @var{y}, @var{y}, @var{fmt})
+## @end example
+##
+## If the @var{fmt} argument is supplied, it is interpreted as
+## follows.  If @var{fmt} is missing, the default gnuplot line style
+## is assumed.
+##
+## @table @samp
+## @item -
+## Set lines plot style (default).
+##
+## @item .
+## Set dots plot style.
+##
+## @item @@
+## Set points plot style.
+##
+## @item -@@
+## Set linespoints plot style.
+##
+## @item ^
+## Set impulses plot style.
+##
+## @item L
+## Set steps plot style.
+##
+## @item @var{n}
+## Interpreted as the plot color if @var{n} is an integer in the range 1 to
+## 6.
+##
+## @item @var{nm}
+## If @var{nm} is a two digit integer and @var{m} is an integer in the
+## range 1 to 6, @var{m} is interpreted as the point style.  This is only
+## valid in combination with the @code{@@} or @code{-@@} specifiers.
+##
+## @item @var{c}
+## If @var{c} is one of @code{"k"}, @code{"r"}, @code{"g"}, @code{"b"},
+## @code{"m"}, @code{"c"}, or @code{"w"}, it is interpreted as the plot
+## color (black, red, green, blue, magenta, cyan, or white).
+##
+## @item ";title;"
+## Here @code{"title"} is the label for the key.
+##
+## @item +
+## @itemx *
+## @itemx o
+## @itemx x
+## Used in combination with the points or linespoints styles, set the point
+## style.
+## @end table
+##
+## The color line styles have the following meanings on terminals that
+## support color.
+##
+## @example
+## Number  Gnuplot colors  (lines)points style
+##   1       red                   *
+##   2       green                 +
+##   3       blue                  o
+##   4       magenta               x
+##   5       cyan                house
+##   6       brown            there exists
+## @end example
+##
+## The @var{fmt} argument can also be used to assign key titles.
+## To do so, include the desired title between semi-colons after the
+## formatting sequence described above, e.g. "+3;Key Title;"
+## Note that the last semi-colon is required and will generate an error if
+## it is left out.
+##
+## Arguments can also be given in groups of three as
+##
+## @example
+## plot3 (@var{x1}, @var{y1}, @var{y1}, @var{x2}, @var{y2}, @var{y2}, @dots{})
+## @end example
+## 
+## @noindent
+## where each set of three arguments are treated as seperate lines or
+## sets of lines in three dimensions.
+##
+## An example of the use of plot3 is
+##
+## @example
+## @group
+##    z = [0:0.05:5];
+##    plot3(cos(2*pi*z), sin(2*pi*z), z, ";helix;");
+## @end group
+## @end example
+##
+## @seealso{plot, semilogx, semilogy, loglog, polar, mesh, contour, __pltopt__
+## bar, stairs, errorbar, replot, xlabel, ylabel, title, print}
+## @end deftypefn
+
+## Author: Paul Kienzle
+##         (modified from __plt__.m)
+
+function plot3(varargin)
+
+  hold_state = ishold ();
+  
+  unwind_protect
+
+    x_set = 0;
+    y_set = 0;
+    z_set = 0;
+    
+    ## Gather arguments, decode format, and plot lines.
+    for arg = 1:length(varargin)
+      new = varargin{arg};
+      
+      if (ischar (new))
+	if (! z_set)
+	  error ("plot3: needs x, y, z");
+	endif
+	fmt = __pltopt__ ("plot3", new);
+	__plt3__(x, y, z, fmt);
+	hold on;
+	x_set = 0;
+	y_set = 0;
+	z_set = 0;
+      elseif (!x_set)
+	x = new;
+	x_set = 1;
+      elseif (!y_set)
+	y = new;
+	y_set = 1;
+      elseif (!z_set)
+	z = new;
+	z_set = 1;
+      else
+	__plt3__ (x, y, z, "");
+	hold on;
+	x = new;
+	y_set = 0;
+	z_set = 0;
+      endif
+       
+    endfor
+    
+    ## Handle last plot.
+    
+    if  (z_set)
+      __plt3__ (x, y, z, "");
+    elseif (x_set)
+      error ("plot3: needs x, y, z");
+    endif
+    
+  unwind_protect_cleanup
+    
+    if (! hold_state)
+      hold off;
+    endif
+    
+  end_unwind_protect
+
+endfunction