How do I fix this error?

deltat=0.1;
nsamples=2^10;
fs=1/deltat;
time=[0 : deltat : deltat*(nsamples-1)];
psdtot(1:nsamples/2+1) = zeros(1,nsamples/2+1);
nblock = 10;
for k=1:nblock
for i=1: nsamples
ydata(i,:) =5+10*cos(2*pi*time+pi/6)+15* randn(1);
end
[pxx,f] = periodogram(ydata,rectwin(nsamples),nsamples,fs);
size(psdtot)
size(pxx)
psdtot = psdtot + pxx/nblock;

end

ans = 1x2

1 513

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ans = 1x2

513 1024

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Arrays have incompatible sizes for this operation.

figure(1);
plot(time,ydata);

I'm trying to generate Gaussian noise from x(t)=5+10*cos(2*pi*t+pi/6)+G(sigma,t)

G(sigma,t) is Gaussian noise with a standard deviation of 15 (sigma G=15), detat=0.1(s), and nsample=2^10.

It is the start of calculating Power Spectral Density with FFT.

The overall variance of the signal is (sigma g)^2+(A)^2/2 as expected.

The generated random signal should be sinusoidal because X(t) has the cosine factor.

[Torsten]

You cannot add arrays of size 1x513 and 513x1024 (see above).

Answer 1

[cui,xingxing]

You should make sure that the array dimensions in the arithmetic are consistent, for example I changed your psdtot variable to a column vector. As far as I remember, matlab supports automatic dimension expansion since R2016a/b.

deltat=0.1;
nsamples=2^10;
fs=1/deltat;
time=[0 : deltat : deltat*(nsamples-1)];
psdtot(1:nsamples/2+1) = zeros(1,nsamples/2+1);
psdtot = psdtot(:); % here
nblock = 10;
for k=1:nblock
    for i=1: nsamples
        ydata(i,:) =5+10*cos(2*pi*time+pi/6)+15* randn(1);
    end
    [pxx,f] = periodogram(ydata,rectwin(nsamples),nsamples,fs);
    psdtot = psdtot + pxx/nblock;
end

figure(1);
plot(time,ydata);

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[Derek]

So using this data provided how do you plot the psd vs frequency? In a log log plot. Do you have to do the fgts prior to the peridogram