FFT plot in frequency domain, error help

Hi,

I did a myfft function in order to plot the (PSD,f) of a signal: 10696x1 double

[f, ~, ~, psd, ~] = myfft(Data, fs); 

function [f, amplitude, phase, PSD, power] = myfft(signal, samplingRate)

if ~isempty(signal)
Fs = samplingRate;
T = 1/Fs;
L = length(signal);
t = (0:L-1)*T; 

Y = fft(signal);

P2 = abs(Y);
P1 = P2(1:floor(L/2)+1,:);
P1(2:end-1,:) = 2*P1(2:end-1,:);
f = Fs*(0:(L/2))/L;
amplitude = P1;
phase = unwrap(angle(Y));
phase = phase(1:floor(L/2)+1,:);

% Power Spectrum
PSD = Y.*conj(Y);
PSD = (1/(Fs*L)) .* PSD(1:floor(L/2)+1,:);
PSD(2:end-1,:) = 2*PSD(2:end-1,:);

power = sum(PSD);
else
f = [];
amplitude = [];
phase = [];
power = NaN;
PSD = [];
end

I get this error:

% Error using  * 
% Incorrect dimensions for matrix multiplication. Check that the number of columns in the first matrix matches the
% number of rows in the second matrix. To perform elementwise multiplication, use '.*'.

% Error in myfft (line 10)
% t = (0:L-1)*T; % signal duration (time vector)

% Error in s (line 19)
% [f, ~, ~, psd, ~] = myfft(Data, fs); ;

Can you please help?

Thank you in advance!

Answer 1

[Dave B]

What is size(Data) and size(fs)? Your function doesn't error for me when I give it a scalar fs and a vector signal:

load handel.mat
size(y)

ans = 1×2

73113 1

size(Fs)

ans = 1×2

1 1

[f, ~, ~, psd, ~] = myfft(y, Fs); 
plot(f,psd)

function [f, amplitude, phase, PSD, power] = myfft(signal, samplingRate)
    if ~isempty(signal)
        Fs = samplingRate;
        T = 1/Fs;
        L = length(signal);
        t = (0:L-1)*T; 
        Y = fft(signal);
        P2 = abs(Y);
        P1 = P2(1:floor(L/2)+1,:);
        P1(2:end-1,:) = 2*P1(2:end-1,:);
        f = Fs*(0:(L/2))/L;
        amplitude = P1;
        phase = unwrap(angle(Y));
        phase = phase(1:floor(L/2)+1,:);
        % Power Spectrum
        PSD = Y.*conj(Y);
        PSD = (1/(Fs*L)) .* PSD(1:floor(L/2)+1,:);
        PSD(2:end-1,:) = 2*PSD(2:end-1,:);
        power = sum(PSD);
    else
        f = [];
        amplitude = [];
        phase = [];
        power = NaN;
        PSD = [];
    end
end

[Nina Perf]

Thanks! That worked