function[AMP, freq, phase] = mcmc(A,f,phi,AMP,freq,phase,z,k) 
% step is the step size
step = 0.01 + exp(-k/1000);
counteramp=0;
while counteramp == 0
Anew = abs(A + 0.5*step*randn);
if Anew>=1
    counteramp=1;
end
end
counterfreq=0;
while counterfreq ==0
fnew = abs(f + (step/100)*randn);
if fnew >= 0.01
    counterfreq=1;
end
end
counterphi = 0;
while counterphi ==0
           phinew = abs(phi +2*pi*step*randn);
       if (phinew > 0) & (phinew <2*pi)
           counterphi = 1;
       end
end
oldprob = probabilityphi(AMP,freq,phase);
trialA=AMP;trialf=freq;trialphi=phase;
trialA(1,z)=Anew;trialf(1,z)=fnew;trialphi(1,z)=phinew;
newprob = probabilityphi(trialA,trialf,trialphi);
if (newprob-oldprob) > 0
    AMP = trialA;freq=trialf;phase=trialphi;
else 
    if ((k>0)& ((newprob/oldprob)>=rand))
      AMP = trialA;freq=trialf;phase=trialphi;
    end
end