findcriticalpoints.m

最新的HHT时频分析程序By Huang and Wu

function [allx, ally] = findcriticalpoints(datay)
%
% [allx, ally] = findcriticalpoints(datay):
%
% The function FINDCRITICALPOINTS returns max, min and zero crossing values
% and their coordinates in the order found in datay(n),
% where n specifies the dimension of array datay.
% The value datay(i) is considered to have a local minimum in i,
% if datay(i-1) > datay(i) < datay(i+1);
% The value datay(i) is considered to have a local maximum in i,
% if datay(i-1) < datay(i) > datay(i+1);
% The value datay(i) is considered to have a zero crossing, if
% datay(i) and datay(i+1) have different signs. The coordinate
% of datay(i) is linearly interpolated.
%
% Input-
%	datay	- input vector of values
% Output-
%	allx	- vector that specifies the coordinates of max, min
%		    and zero crossing values in the order found
%	ally	- corresponding max, min and zero values
%
% Karin Blank (NASA GSFC)	    March 26, 2003  Initial
% Jelena Marshak (NASA GSFC)	July 16, 2004 Modified
%	(Replaced '&&' by '&' in zero-crossing calculation section.)
%	(Corrected zero-crossing calculation.)
%
% Notes-
% Used by FAZ, FAZPLUS