How to find frequency components from a signal?

How to find frequency components from a signal?

[SUMIT]

Actually I want to find frequency components from a gas sensor output signal.. can any one help me..?

Answer 1

[Carlos]

Your question is perhaps too generic, however to find frequency components of a signal in Matlab the FFT command is braodly used.Have a look here

http://www.mathworks.es/es/help/matlab/ref/fft.html

[SUMIT]

Actually I want to find frequency components from a gas sensor output signal.. can any one help me..?

[Carlos]

Can you give us some more insight about your signal? Do you know your signals'sampling frequency? Can you attach the data?

[SUMIT]

I am ataching the excel sheet of data. Here the 1st coloumn is time and 2nd coloumn is corresponding data.I want to know what are the frequency components present. Please help with the matlab code.

[Carlos]

Do you know something about your signals' sampling frequency?

[SUMIT]

No I dont know, but can it be make out from the real time axis coloumn that i have given in the excel sheet?

[SUMIT]

1st column which is the time axis is in seconds.

[Carlos]

I cannot open the file.Could you pass me the file in .mat format?

[SUMIT]

I am ataching the data in .mat format and sampling frequency 50Hz .

[Carlos]

Try this

      >> x=data;
      >> Fs=50;
      >>L=length(x);
      >>NFFT = 2^nextpow2(L);
      >>f = Fs/2*linspace(0,1,NFFT/2+1);
      >> x=data;
      >> Fs=50;
      >> L=length(x);
      >> NFFT = 2^nextpow2(L);
      >> f = Fs/2*linspace(0,1,NFFT/2+1);
      >> Y = fft(x,NFFT)/L;
      >> plot(f,2*abs(Y(1:NFFT/2+1))) 
      title('Single-Sided Amplitude Spectrum of y(t)')
      xlabel('Frequency (Hz)')
      ylabel('|Y(f)|')

[Prerana Gawale]

I tried this approach and I'm getting 0Hz frequency. Please find attached data. The data duration is 15.763 secs.

Answer 2

[Manthan Unecha]

clear all;
clc;

i=sqrt(-1);
e=exp(1);
F=input('Input X and Y in matrix form (nX2) = ');

Unable to run the 'fevalJSON' function because it calls the 'input' function, which is not supported for this product offering.

tmp=size(F);
N=tmp(1,1)
F_sample=1/(F(3,1)-F(2,1))
x=[];
y=[];
for k=0:1:120
    x=[x k];
    f=0;
    for j=1 : N
        f=f + F((j),2)*e^(-i*2*pi*k*(j)/N);
    end
    f=abs(f);
    y=[y f];
end
plot(x,y);
% stem(x,y);