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')
