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scripts/plot/fplot.m

changeset 10289: 4b124317dc38
parent:dbd0c77e575e
author: John W. Eaton <jwe@octave.org>
date: Tue Feb 09 20:58:55 2010 -0500 (55 minutes ago)
permissions: -rw-r--r--
description: base_properties::set_children: account for hidden children 
     1## Copyright (C) 2005, 2006, 2007, 2008, 2009 Paul Kienzle

     2##

     3## This file is part of Octave.

     4##

     5## Octave is free software; you can redistribute it and/or modify it

     6## under the terms of the GNU General Public License as published by

     7## the Free Software Foundation; either version 3 of the License, or (at

     8## your option) any later version.

     9##

    10## Octave is distributed in the hope that it will be useful, but

    11## WITHOUT ANY WARRANTY; without even the implied warranty of

    12## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

    13## General Public License for more details.

    14##

    15## You should have received a copy of the GNU General Public License

    16## along with Octave; see the file COPYING.  If not, see

    17## <http://www.gnu.org/licenses/>.

    18

    19## -*- texinfo -*-

    20## @deftypefn {Function File} {} fplot (@var{fn}, @var{limits})

    21## @deftypefnx {Function File} {} fplot (@var{fn}, @var{limits}, @var{tol})

    22## @deftypefnx {Function File} {} fplot (@var{fn}, @var{limits}, @var{n})

    23## @deftypefnx {Function File} {} fplot (@dots{}, @var{fmt})

    24## Plot a function @var{fn}, within the defined limits.  @var{fn}

    25## an be either a string, a function handle or an inline function.

    26## The limits of the plot are given by @var{limits} of the form

    27## @code{[@var{xlo}, @var{xhi}]} or @code{[@var{xlo}, @var{xhi},

    28## @var{ylo}, @var{yhi}]}.  @var{tol} is the default tolerance to use for the

    29## plot, and if @var{tol} is an integer it is assumed that it defines the 

    30## number points to use in the plot.  The @var{fmt} argument is passed

    31## to the plot command.

    32##

    33## @example

    34## @group

    35##    fplot ("cos", [0, 2*pi])

    36##    fplot ("[cos(x), sin(x)]", [0, 2*pi])

    37## @end group

    38## @end example

    39## @seealso{plot}

    40## @end deftypefn

    41

    42## Author: Paul Kienzle <pkienzle@users.sf.net>

    43

    44function fplot (fn, limits, n, linespec)

    45  if (nargin < 2 || nargin > 4)

    46    print_usage ();

    47  endif

    48

    49  if (nargin < 3) 

    50    n = 0.002; 

    51  endif

    52

    53  have_linespec = true;

    54  if (nargin < 4) 

    55    have_linespec = false;

    56  endif

    57

    58  if (ischar (n))

    59    have_linespec = true;

    60    linespec = n;

    61    n = 0.002;

    62  endif

    63

    64  if (strcmp (typeinfo (fn), "inline function"))

    65    fn = vectorize (fn);

    66    nam = formula (fn);

    67  elseif (isa (fn, "function_handle"))

    68    nam = func2str (fn);

    69  elseif (all (isalnum (fn)))

    70    nam = fn;

    71  else

    72    fn = vectorize (inline (fn));

    73    nam = formula (fn);

    74  endif

    75

    76  if (floor(n) != n)

    77    tol = n;

    78    x0 = linspace (limits(1), limits(2), 5)';

    79    y0 = feval (fn, x0);

    80    err0 = Inf;

    81    n = 8;

    82    x = linspace (limits(1), limits(2), n)';

    83    y = feval (fn, x);

    84

    85    while (n < 2 .^ 20)

    86      y00 = interp1 (x0, y0, x, "linear");

    87      err = 0.5 * max (abs ((y00 - y) ./ (y00 + y))(:));

    88      if (err == err0 || 0.5 * max (abs ((y00 - y) ./ (y00 + y))(:)) < tol)

    89	break;

    90      endif

    91      x0 = x;

    92      y0 = y;

    93      err0 = err;

    94      n = 2 * (n - 1) + 1;

    95      x = linspace (limits(1), limits(2), n)';

    96      y = feval (fn, x);

    97    endwhile 

    98  else

    99    x = linspace (limits(1), limits(2), n)';

   100    y = feval (fn, x);

   101  endif

   102

   103  if (have_linespec)

   104    plot (x, y, linespec);

   105  else

   106    plot (x, y);

   107  endif

   108

   109  if (length (limits) > 2) 

   110    axis (limits);

   111  endif

   112

   113  if (isvector (y))

   114    legend (nam);

   115  else

   116    for i = 1:columns (y)

   117      nams{i} = sprintf ("%s(:,%i)", nam, i);

   118    endfor

   119    legend (nams{:});

   120  endif

   121endfunction

   122

   123%!demo

   124%! fplot ("cos", [0, 2*pi])

   125

   126%!demo

   127%! fplot ("[cos(x), sin(x)]", [0, 2*pi])