fft Invalid expression in plot

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Alia Hicks
Alia Hicks on 28 Jul 2020
Answered: Alia Hicks on 28 Jul 2020
I'm recieving error "Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters." at the second from last line "plot(t,f,); %amp vs time"
dt = .001;
t = 0:dt:1;
f = data_output;
%%Compute the Fast Fourier Transform FFT
n = length(t);
fhat = fft(f,n); % Compute the fast Fourier transform
PSD = fhat.*conj(fhat)/n; % Power spectrum (power per freq)
freq = 1/(dt*n)*(0:n); % Create x-axis of frequencies in Hz
L = 1:floor(n/2); % Only plot the first half of freqs
%%Use the PSD to filter out noise
indices = PSD>100; % Find all freqs with large power
PSDclean = PSD.*indices; % Zero out all others
fhat = indices.*fhat; % Zero out small Fourier coeffs. in Y
ffilt = ifft(fhat); % Inverse FFT for filtered time signal
%%PLOTS
plot(t,f,); %amp vs time
plot(f,fft); % mag vs freq

Accepted Answer

madhan ravi
madhan ravi on 28 Jul 2020
plot(t, f)

More Answers (1)

Alia Hicks
Alia Hicks on 28 Jul 2020
Thanks for your answer Madhan Ravi. I've rewritten it, " plot(t, f), hold on
plot (f, fft);" Now I get the error,
"Error using plot
Vectors must be the same length.
Error in Julytwentyseventh (line 21)
plot(t, f), hold on"

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