Plotting amplitude spectrum of a signal

So I need to generate a segment of 95 Hz sine wave for the duration of 35 ms, with 3.5 kHz sampling rate and display it in 2 graphs, time domain and amplitude spectrum.

I am struggling with amplitude spectrum, I imagine function fft is required, but how should it be used in this case?

Thanks in advance!

Here is my code below for representation in time domain:

   Fs = 3500;                   % samples per second
   dt = 1/Fs;                   % seconds per sample
   StopTime = 0.35;             % seconds
   t = (0:dt:StopTime-dt)';     % seconds
   %%Sine wave:
   Fc = 95;                     % hertz
   x = cos(2*pi*Fc*t);
   % Plot the signal versus time:
   plot(t,x);
   xlabel('Time(S)');
   title('Signal versus Time');

Answer 1

[Ameer Hamza]

Try the following code. Also see the first example on the documentation page of ff() for more details.

Fs = 3500;                   % samples per second
dt = 1/Fs;                   % seconds per sample
StopTime = 0.35;             % seconds
t = (0:dt:StopTime-dt)';     % seconds
%%Sine wave:
Fc = 95;                     % hertz
x = cos(2*pi*Fc*t);

% Plot the signal versus time:
subplot(2,1,1);
plot(t,x);
xlabel('Time(S)');
title('Signal versus Time');

subplot(2,1,2);
f = Fs*linspace(0, 1/2, floor(numel(x)/2));
fr = fft(x);
fr = abs(fr)/numel(x);
fr = fr(1:floor(end/2));
fr(2:end-1) = 2*fr(2:end-1);
plot(f, fr);
xlabel('Time(S)');
title('Frequency Response');

[Ian Cobb]

shouldnt the x axis of the second plot be frequency in Hz?

[Paul]

Yes, it should

Answer 2

[Mehmed Saad]

https://in.mathworks.com/matlabcentral/answers/21096-amplitude-spectrum

Answer 3

[Sady]

Fs = 3500; % samples per second

dt = 1/Fs; % seconds per sample

StopTime = 0.35; % seconds

t = (0:dt:StopTime-dt)'; % seconds

%%Sine wave:

Fc = 95; % hertz

x = cos(2*pi*Fc*t);

% Plot the signal versus time:

subplot(2,1,1);

plot(t,x);

xlabel('Time(S)');

title('Signal versus Time');

subplot(2,1,2);

f = Fs*linspace(0, 1/2, floor(numel(x)/2));

fr = fft(x);

fr = abs(fr)/numel(x);

fr = fr(1:floor(end/2));

fr(2:end-1) = 2*fr(2:end-1);

plot(f, fr);

xlabel('Time(S)');

title('Frequency Response');