N = 250;
x = floor(datenum(now))-100+(1:N)/10; % 10 mælingar á dag
xd = datestr(x,'dddd');
y = 20+10*cosd(360*x) + randi(10,1,N);
xx = mod(x,1); % skiljum aukastafina eftir
timabil = [12,13]; % 12:00-13:00
dagur = 3; % þriðjudagur
ind1 = xx >= timabil(1)/24 & xx <= timabil(2)/24;
ind2 = weekday(x) == dagur;
ind3 = ind1 & ind2;
plot(x,y);
hold on
plot(x(ind3),y(ind3),'o');

ygaur = mean(y(ind3));