matlab中contour函数的返回值contour matrix C如何使用

function s=contourdata(c)

% S = CONTOURDATA(C) extracts the (x,y) data pairs describing each contour
% line and other data from the contour matrix C. The vector array structure
% S returned has the following fields:
%
% S(k).level contains the contour level height of the k-th line.
% S(k).numel contains the number of points describing the k-th line.
% S(k).isopen is True if the k-th contour is open and False if it is closed.
% S(k).xdata contains the x-axis data for the k-th line as a column vector.
% S(k).ydata contains the y-axis data for the k-th line as a column vector.
%
% For example: PLOT(S(k).xdata,S(k).ydata)) plots just the k-th contour.

if nargin<1 || ~isfloat(c) || size(c,1)~=2 || size(c,2)<4
error('CONTOURDATA:rhs',...
'Input Must be the 2-by-N Contour Matrix C.')
end

tol=1e-12;
k=1; % contour line number
col=1; % index of column containing contour level and number of points

while col<size(c,2); % while less than total columns in c
s(k).level = c(1,col); %#ok
s(k).numel = c(2,col); %#ok
idx=col+1:col+c(2,col);
s(k).xdata = c(1,idx).'; %#ok
s(k).ydata = c(2,idx).'; %#ok
s(k).isopen = abs(diff(c(1,idx([1 end]))))>tol || ...
abs(diff(c(2,idx([1 end]))))>tol; %#ok
k=k+1;
col=col+c(2,col)+1;
end