calculate frequency energy from spectrum signal

[Adnan86]

calculate frequency energy from spectrum signal in MATLAB

I am trying to calculat the energy spectrum of a signal in MATLAB.
for example I want calculate this ratio :
(low frequency energy (1 hz to 2 hz)) / (high frequency energy (4 hz to 5 hz)) in the spectrum of the discrete signal .

But, I have no idea how to get energy-Hz for each frequency components.

Any help is much appreciated !

 

[andre_luis]

The FFT algorithm don´t meet to what you are asking for ?


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[Adnan86]

at first we use FFT and then for get energy of signal we us SUM of square like this :

SS = Zigma[ (abs(FFT_Siagnal)).^2]

but SS it's energy of whole of signal . but i want enrgy of signal between for example 2 hz to 3 hz .
so haw i can do that ?

 

[andre_luis]

I could not find some reference about the Zigma function.
Can you place here the entire code ?



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[Adnan86]

%PSD
 
 FFT_HR_Siagnal = fft(HR_Siagnal,N);
 
 
 Square_HR_Siagnal = (abs(FFT_HR_Siagnal)).^2 ;
 % N,M should determin as Frequence but how ? I dont know !!!
 Energy_low = 0 ;
 for i= N1: N2
     Energy_low = Square_HR_Siagnal(i) + Energy_low ;
 end ;
%  subplot(1 2 1 ) ;
%  plot (Energy_low) ;
 
 Energy_high = 0 ;
 for i= M1:M2
     Energy_high = Square_HR_Siagnal(i) + Energy_high ;
 end ;
 
 AB = Energy_low / Energy_high ;

 

[andre_luis]

I tried simulate, but gave this error:

??? Undefined function or variable 'HR_Siagnal'.

Post here HR_Siagnal data.






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[Adnan86]

this is signal

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instead N in first row use this :
FFT_HR_Siagnal = fft(HR_Siagnal,;