how to use PHD method to compute the frequency estimate?

let x(t)=10cos(200*pi*t+1.2) which is a continuous-time sinusoid. The x(t) is sampled every Ts=0.001 sec. to obtain a sequence x[n] where x[n]=x(nTs) for n between 0 and 100 (including 0 and 100)

im trying to develop the MATLAB function for the PHD estimator, denoted by phd.

given the following: 1.that xcorr with “unbiased” can be utilized in implementing phd.m.

come up with the following code

 function w = phd(x);
% w = phd(x) is used to estimate frequency
% the PHD method from the vector x
% x is supposed to be a noisy single-tone sequence
% w is the estimated frequency in radian
N=max(size(x));
for n=1:N-1
r1=(1/(N-1))*x(n)*x(n+1); 
for n=1:N-2
r2=(1/(N-2))*x(n)*x(n+1);  
t1=0;
t2=0;
t1=r2+((r2)^2+8*(r1)^2)^(1/2);
t2=t2+4/r1;
end
r = t1/t2;
if (r>1)
r=1;
end
if (r<-1)
r=-1;
end
w=acos(r);

now I want to use this phd method to determine the frquency estimate for x[n].

 t = 0:0.001:0.1-0.001;
 x = 10*cos(200*pi*t+1.2);
 N=max(size(x));
for n=1:N-1
r1=(1/(N-1))*x(n)*x(n+1); 
for n=1:N-2
r2=(1/(N-2))*x(n)*x(n+1);  
t1=0;
t2=0;
t1=r2+((r2)^2+8*(r1)^2)^(1/2);
t2=t2+4/r1;
end
r = t1/t2;
if (r>1)
r=1;
end
if (r<-1)
r=-1;
end
w=acos(r);

but no results output, could anyone help to solve? thank u.