如何做一个波形上(极大值点)、下(极小值点) 包络线?
如题,如何做一个波形上(极大值点)、下(极小值点) 包络线?我一点思路都没有,大家帮帮忙啊 搜一下包络线! 论坛上有 本帖最后由 VibInfo 于 2016-10-21 15:25 编辑
原帖由 wzhstone 于 2008-11-23 13:44 发表
如题,如何做一个波形上(极大值点)、下(极小值点) 包络线?
我一点思路都没有,大家帮帮忙啊
转载一个求上下包络的函数:
function = 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.
%
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
%----------------------------------------------------
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);
调试程序
% DEMOENVELOPE shows how to use function envelope to obtain the
% upper/down envelope of a given data and plot the envelope.
%
clc;
% Load a signal waveform
%--------------------------------------------
N = 100;
fs = 50;
t = ((1:N)/512)';
T0 = 0.01;
f0 = 12.7;
T1 = 0.026;
f1 = 35.8
y = exp(-T0*t) .* 5 .* sin(2*pi * f0*t) + exp(-T1*t).*4.*sin(2*pi*f1*t);
%load data.txt data;
%t = data(:,1); % time series
%y = data(:,2); % signal data
figure(1);
plot(t,y,'b-');
title('The original signal waveform','FontSize',18);
% Call function envelope to
% obtain the envelope data
%--------------------------------------------
= envelope(t,y,'linear');
% Show the envelope alone
%--------------------------------------------
figure(2)
plot(t,up); hold on;
plot(t,down);
title('The envelope of the given signal data','FontSize',18);
hold off;
% Show the original signal and its envelope
%--------------------------------------------
figure(3)
plot(t,y,'g-'); hold on;
plot(t,up,'r-.');
plot(t,down,'r-.');
title('The envelope vs the given signal data','FontSize',18);
hold off;
[ 本帖最后由 songzy41 于 2008-11-23 17:08 编辑 ] 若有重复点即发生一些小问题, 各位大大对如何解决是否有好意见?
http://forum.vibunion.com/forum/thread-32967-2-1.html 回复 3 # songzy41 的帖子
您好，你现在还做这个吗? 我只知道这个是用三次插值做的，可以用函数spline……不知道对你是不是有帮助
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