Develop a program along the lines of Example 2.11 to determine the correlation in heart rate variability during meditation. Load file Hr_med.mat which contains the heart rate in variable hr_med and the time vector in variable t_med. Calculate and plot the autocovariance. The result will show that the heart rate under meditative conditions contains some periodic elements. Can you determine the frequency of these periodic elements? A more definitive approach is presented in the next chapter which shows how to identify the frequency characteristics of any waveform

% Example 2.11 Use of autocovariance to determine the correlation % of heart rate variation between heart beats % load Hr_pre; % Load normal HR data [cov_pre,lags_pre] = axcor(hr_pre - mean(hr_pre)); % Auto-covariance plot(lags_pre,cov_pre,k); hold on; % Plot normal auto-cov plot([lags_pre(1) lags_pre(end)], [0 0],k); % Plot a zero line axis([-30 30 -0.2 1.2]); % Limit x-axis to 30 beats