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wsmwsj

新虫 (初入文坛)

应助: 0 (幼儿园)
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在线: 51分钟
虫号: 1090546
注册: 2010-09-06

[交流] 【求助】信号包络仿真已有1人参与

请求好心人给我看看下面有关信号包络的程序运行为什么会出错？
我输入：x=0:10；
            y=cos(x);
            envelope(x,y,spline)
总是会出现x没有定义呢
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(横坐标) of the given data
% y             the ordinate(纵坐标) of the given data
% interpMethod the interpolation method(内插法)
%
% 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, <WangLeiBox@hotmail.com>, 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.');
end

if (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(找到极大值及相应的下标)
%----------------------------------------------------
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(找到极小值及相应的下标)
%----------------------------------------------------
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);

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