How can I plot convolution of rect(t/2)*sgn(t)

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courtney 2012-8-31

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The exercise I am trying to complete requires me to: Compute and plot the following convolution integral by using "conv.m" in MATLAB. rect(t/2)*sgn(t)

CODE 1 t=-5:0.01:5; 2 x=abs(t)<1; 3 h=sign(t); 4 y=conv(x,h); 5 plot(t,y);

ERRORS Error using conv2 First and second arguments must be single or double.

Error in conv (line 39) c = conv2(a(:),b(:),shape);

Error in three (line 4) y = conv(x,h);

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Azzi Abdelmalek 2012-8-31

在 MATLAB Online 中打开

what is

2 x=abs(t)<1

courtney 2012-9-1

x=abs(t)<1 gives the equivalent of rect(t/2) where: rect(t) = [ 1, abs(t) < 0.5 & [ 0, abs(t) > 0.5 as piecewise fucntion.

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Answer 1

Star Strider 2012-9-1

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在 MATLAB Online 中打开

You have to make the small adjustment of plotting every other value of y (since y is about twice the length of t), but if you want to plot y as a function of t, this will work:

        t = -5:0.01:5;
        x = double(abs(t) < 1));    % Convert logical to double
        h = sign(t);
        y = conv(x,h);
        figure(1)
        plot(t,y(1:2:end))          % Plot every other value of y

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courtney 2012-9-2

I ended up getting the correct answer using this code but your method worked as well Strider. Cheers for the help!

(the rect(t) here is referring to a function out file)

t = -6:0.01:6;

x = rect(t);

y = sign(t);

z = conv(x,y)*0.001;

plot(-12:0.01:12,z);

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Answer 2

Azzi Abdelmalek 2012-8-31

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t=-5:0.01:5;
x=abs(t); 
h=sign(t); 
[tt,y]=conv(x,h); 
plot(y);   % y and t have'nt the same length

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courtney 2012-9-1

编辑：courtney 2012-9-1

在 MATLAB Online 中打开

If I try to run this I get the following errors.

Error using conv Too many output arguments.

Error in test [tt,y]=conv(x,y);

Instead of using 'x=abs<1' for the equivalent of rect(t/2) I created a function out file called rect.m with the following code

function[out]=rect(t);

for i=1:length(t);

    if(abs(t(i))<1)
        out(i)=1;
    else;
        out(i)=0;
    end
end

Referring to this code in my convolution file gives me the perfect rect(t/2) plot but I still get the following error.

Error using plot

Vectors must be the same lengths.

Azzi Abdelmalek 2012-9-1

beacause y and t have'nt the same length. x , h and t have the same length but not with y=conv(x,h) . then instead of plot(t,y) which is false, use plot(y)

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Answer 3

daltonicox 2013-9-13

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how can i plot this: g(t) = rect(t/2) * [δ(t+2) - δ(t+1)]. As matter of fact, i want to plot the convolution of this functions. But i'm having trouble creating the rect function. If anyone can help me, i would appreciate it very much.