peaks and valleys plot

[Rick T]

Greetings All

I'm trying to have the x value and y value next to the peak and valley on a plot can someone assist

t= linspace(0,2*pi,8000); 
freq=10;
y=sin(t*freq)+cos(t*freq*1.3); 
y=y';

y2=y*3+y*4+y*2;
yf=(y2(:,1)/max(abs(y2(:,1)))*1); %keep at 1, amplitude levels 
plot(yf)

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