ifft plot time domain

Question

Blanca Castells 2017-4-5

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https://ww2.mathworks.cn/matlabcentral/answers/333761-ifft-plot-time-domain

评论： roni cohen 2020-11-30

Hello!

I'mt trying to plot an Inverse Fast Fourier Transform. In my case, I have a function handle F(w) where w(omega) is the frequency. If I, for example, give values to omega like w=0:0.01:100, I can get values of F(w), and I have to apply the ifft command to those values:

F=@(w) ... ; %Function handle
w=0:0.01:100;
f=F(w); %Now that's a vector
x=ifft(f); %it returns a vector too

So, if I wanna plot F(w) I use plot(w,f); but if I wanna plot x(t) I only have the vector 'x' but not the time domain to have the x-axis. It's like I have the values of the x(t) function, but I don't know the points they correspond to.

I'd appreciate any help, Thanks! :)

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Answer 1

Jayaram Theegala 2017-4-7

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The time points matter only if you are thinking of a signal in continuous domain. The "ifft" function gives you discrete values and you can plot them as shown below:

plot(1:length(x), x);

However, if you want to convert your discrete signal to continuous domain, you should know the sampling frequency used to create the initial discrete signal. I hope this helps!