findmax.m

本书是电子通信类的本科、研究生辅助教材

function [gt,d]=findmax(data, flag)
%FINDMAX Interpolates the maxima in a vector of data.
%
%	Function used for returning all the maxima in a set of
%	data (vector or matrices). The maxima are calculated by
%	cubic or quadratic interpolation.
[m,n]=size(data);
if nargin < 2, flag = 1; end
% 1-D
d = [2, 2];
if m==1 | n==1
	data=data(:);
	n=max([n,m]);
	ind=find( (data>[data(1)-1;data(1:n-1)]) & (data>=[data(2:n);data(n)-1]) );
	s=length(ind);
	gt=zeros(s,1);
	for i=1:s
		ix=ind(i);
		factor = 1;
		err = 0;  % Smoothness factor
		if (ix==1 | ix==n);
			gt(i)=data(ix);
		elseif ix>n-3 | ix<4
			if data(ix-1)==data(ix)&data(ix+1)==data(ix)
				gt(i)=data(ix);
			else
				gt(i)=quad2(data(ix-1:ix+1));
			end
		elseif data(ix+2)<data(ix+1) 
			[gt(i), err] = cubic(data(ix-1:ix+2), data(ix-2), 0);
		elseif data(ix-2)<data(ix-1) 
			gt(i)=cubic(data(ix-2:ix+1));
		elseif data(ix)>data(ind(i+1))
			gt(i)=quad2(data(ix-1:ix+1));
			factor = 0.75; 
		else
			gt(i)=data(ix);
			factor = 0.5;
		end

% Discretization interval estimation
% Aim: keep error less than 1/10 of abs(constraint) greater than 0
%	or  1/50 of smoothness factor.
% error = data(ix) - gt(i)
		if flag 
			if ~err
				err = data(ix) - gt(i);
			end
			f = abs((gt(i) + 1.1e-5) /(10 * err + 1e-5));
			d(1,1) = min(d(1,1), factor * ((f>=0.3) + (0.7 + f)*(f< 0.3) +(f>1)*(log(f)/100)) );
		end
	end
else
% 2D
	[gt, d] = findmax2(data, flag); 
end
if (m*n)<4, d=[0.5,0.5]; end