Convert data from time domain to the frequency domain using F.T

Hello,

I'm trying to convert my data to the frequency domain. However when I ran my code it says the length dosent match when ploting.

Any help would be much appricated.

load('acceleration.mat');
load('time.mat');

time = time(:,1);
acc_z = accleration(:,3);
N = length(acc_z);

Samp_Interval = mean(diff(time)); % time each datapoint takes 
%disp(Samp_Interval);
Fs = 1/Samp_Interval;             % frequecy sample 

disp(Fs);
Fn = Fs/2;                         % Nyquist frequency 
%disp(Fn);

FT  = fft(acc_z);              
F =(0:1/N:1-1/N)*Fs; 
 %disp(Fv);


% graph 
figure('Name', 'Sensor Data');
axis(1) = subplot(2,1,1);
hold on;
plot(time, accleration(:,3), 'b');
legend('Z');
xlabel('Time (s)');
ylabel('Acceleration (g)');
title('Accelerometer');
hold off;

axis(2) = subplot(2,1,1);
hold on;
plot(Fv,abs(F), 'r');
legend('acc-Z');
xlabel('Frequency (Hz)');
ylabel('Aamplitude)');
title('Frequency domain');

[Divija Aleti]

Hi Kelvin,

The variable 'Fv' has not been defined in your code. Could you check that ?

Answer 1

[Bladi Toaza]

In plot(Fv,abs(F),'r') Fv has not been defined. I think you wanted to plot(FT,abs(F),'r').ç

Just remember the first argument of plot is the X data and the second the Y data. As well check if both vectors X and Y are the same length.