How can i create a FFT/FRF graph using matlab from csv file?

as the title, i want to convert the data to the frequency domain using FFT... and here the csv....which function should i use? tfestimate or fft to generate FRF in order to get the natural frequency....

Answer 1

[KSSV]

clc;
data = csvread('data.csv') ;
t = data(:,1) ;
amp = data(:,2) ;

L = length(t) ;
dt = max(diff(t)) ;
Fs = 1/dt ;
Y = fft(amp);
P2 = abs(Y/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
f = Fs*(0:(L/2))/L;
plot(f,P1) 
title('Single-Sided Amplitude Spectrum of X(t)')
xlabel('f (Hz)')
ylabel('|P1(f)|')
% xlim([0 3000])

[apple fung]

if i got the input and output data should i use tfestimate or fft?

[KSSV]

For fft you have to use fft.

[Mobeen Sohail]

in this code why we used p1(2:end-1)=2*p1(2:end-1). unless in ploting we only used p1 value??

Answer 2

[Piash Das]

Hi, I am having problem to generate FFT from time-domain data of csv file. I can generate values of two variables from the two rows. The first row contains time and the second row contains current. Now I can generate a normal plot. But I want to plot FFT and power spectral density. I got the csv from a simulation (Cadence). there is no fixed step-size of the time values which is problem. Can anyone help me generating FFT and psd? I have attached the file for your convenience.