How should I fix my convolutional integral

Question

Faezeh Manesh 2020-3-9

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/509971-how-should-i-fix-my-convolutional-integral

评论： Steve Chou 2021-3-15

采纳的回答： Matt J

在 MATLAB Online 中打开

Hello all,

Actually, I am trying to convolve two functions (f and y)using the following MATLAB code:

close all;
clear all;
clc;
%set time vector
t0=0;
tf=100;
N=10000;
dt=(tf-t0)/N;
t=t0:dt:tf;
T0=60;
alpha=1;
beta=0.01;
%construct the firxt part of the convolution
for i=1:length(t)
  if(t(i)<=T0)   
    y(i)=0;
  else 
    y(i)=alpha+beta*(t(i)-T0);
  end
end
%plot y(t)
subplot(1,2,1);
plot(t,y,'LineWidth',2);
title('y(t)');
%Second function of the convolution
f2= 0.08787*exp(-((t-63.08)/1.593).^2);
%Convolution of these 2 functions
z=conv(y,f2,'full');
con = z*dt;
subplot(1,2,2);
plot(t,f2,'LineWidth',2);
title('f2');
t = (1:length(con))*dt ;
hold on;
plot(t,con,'LineWidth',2);

I tried to use the guidlines in the following link to run a full convolutional integral :

https://www.mathworks.com/matlabcentral/answers/379866-regarding-calculating-convolution-in-matlab

Here are my results:

This result seems not to be reasonable because both my functions start rising at x=60 but my convolution starts rising at x=120. Can someone helps me with this problem.

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Matt J 2020-3-9

编辑：Matt J 2020-3-9

This result seems not to be reasonable because both my functions start rising at x=60

There's nothing unreasonable about that. That is theoretically what should happen if both functions start at t=60. For the convolution result to start at t=60, you need one of the signals to start at t=0.

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Answer 1

Matt J 2020-3-9

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/509971-how-should-i-fix-my-convolutional-integral#answer_419334

编辑：Matt J 2020-3-9

在 MATLAB Online 中打开

This might be what you want,

subplot(1,2,1);
ty=t;
plot(ty,y,'LineWidth',2);
title('y(t)');
%Second function of the convolution
f2= 0.08787*exp(-((t-63.08)/1.593).^2);
%Convolution of these 2 functions
z=conv(y,f2(find(f2,1):end),'same');
con = z*dt;
subplot(1,2,2);
  plot(ty,f2,'LineWidth',2);
  title('f2');
  hold on;
  tc=linspace(0,1,numel(con));
  tc=tc/tc(2)*dt;
  plot(tc,con,'LineWidth',2);
  hold off