Need to calculate power spectral density of a signal in MATLAB

gauravnanda18 said:

what I have to do is to calculate the noise in a signal and see how it depends on the frequency spectrum. I am trying to calculate PSD of a signal but everytime, I get an error saying "vectors must be the same lengths". I am not able to find a solution.

Here is command which I'm using. please let me know if there is some problem with the command.

I imported the excel file as vectors.

x=time; %time vector in excel file

y=current; %current vector in excel file

plot(x,y); % plot current-time graph

xlabel('time(s)');

ylabel('current(A)');

Fs=50; %sampling frequency

T=1/Fs; %sampling time

L=length; %length of the signal

L1= x/T;

t=(0:L-1)*T; time vector

%%%calculate the mean current

Iavg=mean(L);

%calculate the FFT

NFFT=2^nextpow2(L); %next power of 2 from length y

% calculate and plot PSD of conditioning mode

Nc=abs(fft((y-mean),NFFT)).^2./NFFT; % Nc is power spectral density

Nc = Nc(1:513);

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

fc=Fs/2*linspace(0,1,NFFT/2+1);%frequency

plot(fc,Nc)


ERROR MESSAGE WHICH I GET IS "INDEX EXCEEDS MATRIX DIMENSIONS"

Click to expand...

gauravnanda18 said:

what I have to do is to calculate the noise in a signal and see how it depends on the frequency spectrum. I am trying to calculate PSD of a signal but everytime, I get an error saying "vectors must be the same lengths". I am not able to find a solution.

Here is command which I'm using. please let me know if there is some problem with the command.

I imported the excel file as vectors.

x=time; %time vector in excel file

y=current; %current vector in excel file

plot(x,y); % plot current-time graph

xlabel('time(s)');

ylabel('current(A)');

Fs=50; %sampling frequency

T=1/Fs; %sampling time

L=length; %length of the signal

L1= x/T;

t=(0:L-1)*T; time vector

%%%calculate the mean current

Iavg=mean(L);

%calculate the FFT

NFFT=2^nextpow2(L); %next power of 2 from length y

% calculate and plot PSD of conditioning mode

Nc=abs(fft((y-mean),NFFT)).^2./NFFT; % Nc is power spectral density

Nc = Nc(1:513);

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

fc=Fs/2*linspace(0,1,NFFT/2+1);%frequency

plot(fc,Nc)


ERROR MESSAGE WHICH I GET IS "INDEX EXCEEDS MATRIX DIMENSIONS"

Click to expand...