Time-frequency analysis using spectogram

% Load the measurement signal from a .mat file
x=load('signal27.mat'); 

% Set the parameters for the spectrogram
window_size = 1024; % Size of the analysis window
overlap = window_size/2; % Amount of overlap between windows
nfft = window_size; % Number of FFT points
fs = 1000; % Sampling rate

% Compute the spectrogram
[S, F, T] = spectrogram(x, window_size, overlap, nfft, fs);

% Plot the spectrogram
imagesc(T, F, abs(S));
axis xy;
xlabel('Time (s)');
ylabel('Frequency (Hz)');

WHen trying to run this code, it gives me error on 'pwelch'

Error using pwelch
Expected x to be one of these types:

single, double

Instead its type was struct.

Error in signal.internal.spectral.welchparse>parse_inputs (line 111)
validateattributes(x2,{'single','double'}, {'finite','nonnan'},'pwelch','x')

Error in signal.internal.spectral.welchparse (line 31)
    parse_inputs(x1,esttype,varargin{:});

Error in pspectrogram (line 30)
[xw,nx,~,yw,ny,win,~,~,noverlap,~,~,options] = signal.internal.spectral.welchparse(x,esttype,inpArgs{:});

Error in spectrogram (line 191)
  [varargout{1:nargout}] = pspectrogram({x},'spect',inpArgs{:});

Error in a (line 11)
[S, F, T] = spectrogram(x, window_size, overlap, nfft, fs);

Can anyone suggest what am i doing wrong here?

And also I need to use "spectogram" command to plot images.

Answer 1

[Sulaymon Eshkabilov]

There are a couple of inconsistencies (fs value was incorrect and not read from the signal27.mat) in the code. Here is the corrected code:

% Load the measurement signal from a .mat file
x=load('signal27.mat').y; 
fs = load('signal27.mat').Fs;   % Sampling rate
% Set the parameters for the spectrogram
window_size = 1024; % Size of the analysis window
overlap = window_size/2; % Amount of overlap between windows
nfft = window_size; % Number of FFT points
% Compute the spectrogram
[S, F, T] = spectrogram(x, window_size, overlap, nfft,fs);

% Plot the spectrogram
imagesc(T, F, abs(S));
axis xy;
xlabel('Time (s)');
ylabel('Frequency (Hz)');

figure
spectrogram(x, 'yaxis')