Здравствуйте Andir, Вы писали:

A>Народ подскажите инфу по subj.

A>Постановка задачи:
A>Дано множество точек заданных своими координатами, в каждой точке задано значение некоторого параметра, нужно провести линии равных значений, через определённый шаг.

A>C Уважением, Andir !

Если необходимо выполнить какие-то математические расчеты, я зачастую обращаюсь к пакету MATLAB, к счастью там присутствуют многие алгоритмы, причем в исходниках, правда на своем внутреннем языке M-файлов. Там же и присутствует и такая функция contour, которая выполняет, похоже, именно то, что вам надо. Ниже я привожу ее исходный текст, а также и исходный текст функции contour3, которая используется в тексте contour. Я понимаю, что без должной подготовки ВАм будет трудно понять, как это работает, но если выполнять матемматику вам приходиться часто, то настоятелльно рекомендую выучить этот язык.

function [cout, hand] = contour(varargin)
%CONTOUR Contour plot.
%   CONTOUR(Z) is a contour plot of matrix Z treating the values in Z
%   as heights above a plane.  A contour plot are the level curves
%   of Z for some values V.  The values V are chosen automatically.
%   CONTOUR(X,Y,Z) X and Y specify the (x,y) coordinates of the
%   surface as for SURF.
%   CONTOUR(Z,N) and CONTOUR(X,Y,Z,N) draw N contour lines, 
%   overriding the automatic value.
%   CONTOUR(Z,V) and CONTOUR(X,Y,Z,V) draw LENGTH(V) contour lines 
%   at the values specified in vector V.  Use CONTOUR(Z,[v v]) or
%   CONTOUR(X,Y,Z,[v v]) to compute a single contour at the level v. 
%   [C,H] = CONTOUR(...) returns contour matrix C as described in
%   CONTOURC and a column vector H of handles to LINE or PATCH
%   objects, one handle per line.  Both of these can be used as
%   input to CLABEL. The UserData property of each object contains the
%   height value for each contour. 
%
%   The contours are normally colored based on the current colormap
%   and are drawn as PATCH objects. You can override this behavior
%   with the syntax CONTOUR(...,'LINESPEC') to draw the contours as
%   LINE objects with the color and linetype specified.
%
%   Uses code by R. Pawlowicz to handle parametric surfaces and
%   inline contour labels.
%
%   Example:
%      [c,h] = contour(peaks); clabel(c,h), colorbar
%
%   See also CONTOUR3, CONTOURF, CLABEL, COLORBAR.

%   Additional details:
%
%   CONTOUR uses CONTOUR3 to do most of the contouring.  Unless
%   a linestyle is specified, CONTOUR will draw PATCH objects
%   with edge color taken from the current colormap.  When a linestyle
%   is specified, LINE objects are drawn. To produce the same results
%   as MATLAB 4.2c, use CONTOUR(...,'-').
%
%   Thanks to R. Pawlowicz (IOS) rich@ios.bc.ca for 'contours.m' and 
%   'clabel.m/inline_labels' so that contour now works with parametric
%   surfaces and inline contour labels.

%   Copyright 1984-2000 The MathWorks, Inc. 
%   $Revision: 5.16 $  $Date: 2000/06/02 04:30:44 $

error(nargchk(1,5,nargin));

nin = nargin;
if isstr(varargin{end})
    nin = nin - 1;
end

if nin <= 2,
    [mc,nc] = size(varargin{1});
    lims = [1 nc 1 mc];
else
    lims = [min(varargin{1}(:)),max(varargin{1}(:)), ...
            min(varargin{2}(:)),max(varargin{2}(:))];
end

[c,h,msg] = contour3(varargin{:});
if ~isempty(msg), error(msg); end

for i = 1:length(h)
  set(h(i),'Zdata',[]);
end

if ~ishold
  view(2);
  set(gca,'box','on');
  grid off
end

if nargout > 0
    cout = c;
    hand = h;
end

[code]
function [cout,h,msg] = contour3(varargin)
%CONTOUR3 3-D contour plot.
% CONTOUR3(...) is the same as CONTOUR(...) except that the contours
% are drawn at their corresponding Z level.
%
% C = CONTOUR3(...) returns contour matrix C as described in CONTOURC
% and used by CLABEL.
%
% [C,H] = CONTOUR3(...) returns a column vector H of handles to PATCH
% objects. The UserData property of each object contains the height
% value for each contour.
%
% Example:
% contour3(peaks)
%
% See also CONTOUR, CONTOURF, CLABEL, COLORBAR.

% Additional details:
%
% Unless a linestyle is specified, CONTOUR3 will draw PATCH objects
% with edge color taken from the current colormap. When a linestyle
% is specified, LINE objects are drawn. To produce the same results
% as v4, use CONTOUR3(...,'-').
%
% The order of the handles h relative to the values in cout is used
% in CLABEL to create rotated inline labels. If you change this
% order, you may have to change CLABEL also.

% Clay M. Thompson 3-20-91, 8-18-95
% Modified 1-17-92, LS
% Copyright 1984-2000 The MathWorks, Inc.
% $Revision: 5.16 $ $Date: 2000/06/02 04:30:45 $

error(nargchk(1,5,nargin));
msg = [];

% Check for empty arguments.
for i = 1:nargin
if isempty(varargin{i})
error ('Invalid Argument — Input matrix is empty');
end
end

% Trim off the last arg if it's a string (line_spec).
nin = nargin;
if isstr(varargin{end})
[lin,col,mark,msg] = colstyle(varargin{end});
if ~isempty(msg), error(msg); end
nin = nin — 1;
else
lin = '';
col = '';
end

if nin <= 2,
[mc,nc] = size(varargin{1});
lims = [1 nc 1 mc];
else
lims = [min(varargin{1}(,max(varargin{1}(, ...
min(varargin{2}(,max(varargin{2}(];
end

if isempty(col) % no color spec was given
colortab = get(newplot,'colororder');
[mc,nc] = size(colortab);
end

% Check for level or number of levels N. If it's a scalar and a
% non-zero integer, we assume that it must be N. Otherwise we
% duplicate it so it's treated as a contour level.
if nin == 2 | nin == 4,
if prod(size(varargin{2})) == 1 % might be N or a contour level
if ~(varargin{2} == fix(varargin{2}) & varargin{2})
varargin{2} = [varargin{2},varargin{2}];
end
end
end

% Use contours to get the contour levels.
[c,msg] = contours(varargin{1:nin});
if ~isempty(msg)
if nargout==3,
cout = []; h = [];
return
else
error(msg);
end
end

if isempty(c), h = []; if nargout>0, cout = c; end, return, end

% Create the plot
newplot;
if ~ishold
view(3); grid on
set(gca,'xlim',lims(1:2),'ylim',lims(3:4))
end

limit = size(c,2);
i = 1;
h = [];
color_h = [];
while(i < limit)
z_level = c(1,i);
npoints = c(2,i);
nexti = i+npoints+1;

xdata = c(1,i+1:i+npoints);
ydata = c(2,i+1:i+npoints);
zdata = z_level + 0*xdata; % Make zdata the same size as xdata

% Create the patches or lines
if isempty(col) & isempty(lin),
cu = patch('XData',[xdata NaN],'YData',[ydata NaN], ...
'ZData',[zdata NaN],'CData',[zdata NaN], ...
'facecolor','none','edgecolor','flat',...
'userdata',z_level);
else
cu = line('XData',xdata,'YData',ydata,'ZData',zdata,'userdata',z_level);
end
h = [h; cu(];
color_h = [color_h ; z_level];
i = nexti;
end

if isempty(col) & ~isempty(lin)
% set linecolors — all LEVEL lines should be same color
% first find number of unique contour levels
[zlev, ind] = sort(color_h);
h = h(ind); % handles are now sorted by level
ncon = length(find(diff(zlev))) + 1; % number of unique levels
if ncon > mc % more contour levels than colors, so cycle colors
% build list of colors with cycling
ncomp = round(ncon/mc); % number of complete cycles
remains = ncon — ncomp*mc;
one_cycle = (1:mc)';
index = one_cycle(:,ones(1,ncomp));
index = [index(; (1:remains)'];
colortab = colortab(index,;
end
j = 1;
zl = min(zlev);
for i = 1:length(h)
if zl < zlev(i)
j = j + 1;
zl = zlev(i);
end
set(h(i),'linestyle',lin,'color',colortab(j,;
end
else
if ~isempty(lin)
set(h,'linestyle',lin);
end
if ~isempty(col)
set(h,'color',col);
end
end

% If command was of the form 'c = contour(...)', return the results
% of the contours command.
if nargout > 0
cout = c;
end
[\code]