Dimension error using findpeaks() on Power Spectral Density

I have a set of audio files for which I would like to determine a SNR metric. I tried to implement as follows:

% Calculate the FFT and PSD of each of the signals in the signal vector.
afftvectors = {};
hfftvectors = {};
psdvectors = {};
halffreqvectors = {};
powdbvectors = {};
signalpeaks = {};
signalpeaklocs = {};
noisepsd = {};

for k = 1:numel(signalvectors)
    afy = abs(fft(signalvectors{k}));
    afftvectors{k} = afy;
    % Due to the symmetric nature of FFT, only half the spectrum is actually required.
    hfy = afy(1:length(afy)/2+1);
    hfftvectors{k} = hfy;
    
    py = (1/(freqarray{k} * length(signalvectors{k}))) * abs(hfftvectors{k}).^2;
    % since we take only half of the spectrum, we can conserve the energy by multiplying 
    % by 2. Zero frequency (DC) (index 1) and the Nyquist frequency (last index, i.e, end) 
    % do not occur twice so, we'll skip the multiplication operation on them.
    py(2:end-1) = 2 * py(2:end-1);
    psdvectors{k} = py;
    halffreqvectors{k} = 0:freqarray{k}/length(signalvectors{k}):freqarray{k}/2;
    powdbvectors{k} = 10 * log10(psdvectors{k});
    
    % Find peaks
    [signalpeaks{k},signalpeaklocs{k}] = findpeaks(psdvectors{k});
    noisepsd{k} = psdvectors{k} - signalpeaks{k};
end

So, the idea was to get the peaks of Power Spectral Density vector. I hit a dead end when I got the output where 'signalpeaks{1}' is a vector of size 13235x1 but my 'psdvectors{1}' itself is a vector of size 36001x1. All the elements in cell array 'signalvectors' has a sample size of 72000. What exactly is going wrong here? Am I using the wrong function in findpeaks() or something else needs to be done?

[KSSV]

You can provide the number of peaks you want in findpeaks. So you decide how many peaks you want based on the number of elements in psdvectors.

Or

Think is it possible to interpolation in psdvectors and increase it's size to signalpeaks.

[skrowten_hermit]

Actually, each element in psdvectors has a vector of size 36001x1. So, the number of peaks has to be definitely less than 36001 right? I'm trying to subtract the peaks, which are the actual signal from the power spectral density to get the noise's power spectral density in order to get the SNR. Will interpolation help here?

[KSSV]

As you are subtracting

psdvectors{k} - signalpeaks{k}

they should be of same size.

[skrowten_hermit]

Correct. But they are not the same size here. That is because signalpeaks has more peaks than the data points (here, the frequency) itself. Is that possible?

[Mathieu NOE]

hello

did you tried the matlab snr function already ?

https://www.mathworks.com/help/signal/ref/snr.html