plot discrete time domain signals

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Jinquan Li 2021-2-14

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评论： Paul Hoffrichter 2021-2-15

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Given n=[-1:0.01:10]. Plot the discrete time domain signal: y[n]=e^(-n)*u(n).

Below is my program but i'm not sure if it's correct since this is my fisrt time learning Matlab. Please help. Thanks!

n=-1:0.01:10;

y=exp(-n).*heaviside(n);

stem(t,y)

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Paul 2021-2-14

编辑：Paul 2021-2-15

Be careful using heaviside for u[n]. In control systems and signal processing the function u[n] is the unit step function that is (typically) defined as

u[n] = 1 for n >= 0

u[n] = 0 for n < 0.

However, the default defintion of the heaviside function in Matlab has heaviside(0) = 0.5., which is clearly seen in the plot. Is that the desired answer?

Also, it looks a bit peculiar to have non-integer values of n. Please make sure that's the correct problem statement.

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Paul Hoffrichter 2021-2-14

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在 MATLAB Online 中打开

I recommend using following substitutions:

plot(t,y)
axis( [-1 10 0 1])

Just be careful as to how u(n) is defined. As @Paul mentioned, "heaviside(0) = 0.5., which is clearly seen in the plot. Is that the desired answer?". As you know, e^(-0) is 1, not 0.5, so it is up to you to decide whether your u(n) is defined the way you want it to be defined. If it is a unit step function, where u(0) is 1, then using the heaviside without adjustments leads to an incorrect value for y(n) when n is 0.

Paul Hoffrichter 2021-2-15