Here's a "starter for ten"! I've used approximate time intervals:
T = t(end)/10; % period - there seem to be 10 periods in the range
it = t(t<=T); % times up to one period
dt = numel(it)/2; % number of time points in a half period
n = 20; % total number of half periods
mn = zeros(n,1); % store for minima
mn(end) = min(R1); % last minimum
mx = mn; % store for maxima
mx(1) = 1; % first maximum
% Find sizes of minima and maxima
for i = 2:n
tspan = (i-1)*dt:i*dt;
mn(i-1) = min(R1(tspan));
mx(i) = max(R1(tspan));
end
% Assume "restoration" times occur at half period intervals
% starting at T/4 (an approximation)
Ravpts = (mn+mx)/2;
tavpts = (T/4:T/2:n*T/2);
% Interpolate for "restoration" plot
tav = T/4:t(end);
Rav = interp1(tavpts,Ravpts,tav,'pchip');
% Plots
plot(t,R1,tavpts,Ravpts,'o',tav,Rav,'k--'), grid
xlabel('t'),ylabel('damped sinusoid')
legend('data','restoration points','interpolated restoration')
This is the result:
