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下面是一系列关于MATLAB的包络线的程序：%这是定义了一个函数：function [up,down] = envelope(x,y,interpMethod)%ENVELOPE gets the data of upper and down envelope of the known input (x,y).%% Input parameters:% x the abscissa of the given data% y the ordinate of the given data% interpMethod the interpolation method%% Output parameters:% up the upper envelope, which has the same length as x.% down the down envelope, which has the same length as x.%% See also DIFF INTERP1% Designed by: Lei Wang, , 11-Mar-2003.% Last Revision: 21-Mar-2003.% Dept. Mechanical & Aerospace Engineering, NC State University.% $Revision: 1.1 $ $Date: 3/21/2003 10:33 AM $if length(x) ~= length(y)error('Two input data should have the same length.');endif (nargin < 2)|(nargin > 3),error('Please see help for INPUT DATA.');elseif (nargin == 2)interpMethod = 'linear';end% Find the extreme maxim values% and the corresponding indexes%----------------------------------------------------extrMaxValue = y(find(diff(sign(diff(y)))==-2)+1);extrMaxIndex = find(diff(sign(diff(y)))==-2)+1;% Find the extreme minim values% and the corresponding indexes%----------------------------------------------------extrMinValue = y(find(diff(sign(diff(y)))==+2)+1);extrMinIndex = find(diff(sign(diff(y)))==+2)+1;up = extrMaxValue;up_x = x(extrMaxIndex);down = extrMinValue;down_x = x(extrMinIndex);% Interpolation of the upper/down envelope data%----------------------------------------------------up = interp1(up_x,up,x,interpMethod);down = interp1(down_x,down,x,interpMethod);