a matlab code on adaptive transmit power control on site diversity

function [Gc,Kp,Ti,Td,H]=ziegler(key,vars)
Ti=[]; Td=[]; H=1;
if length(vars)==4,
K=vars(1); L=vars(2); T=vars(3); N=vars(4); a=K*L/T;
if key==1, Kp=1/a;
elseif key==2, Kp=0.9/a; Ti=3.33*L;
elseif key==3 | key==4, Kp=1.2/a; Ti=2*L; Td=L/2; end
elseif length(vars)==3,
K=vars(1); Tc=vars(2); N=vars(3);
if key==1, Kp=0.5*K;
elseif key==2, Kp=0.4*K; Ti=0.8*Tc;
elseif key==3 | key==4, Kp=0.6*K; Ti=0.5*Tc; Td=0.12*Tc; end
elseif length(vars)==5,
K=vars(1); Tc=vars(2); rb=vars(3); N=vars(5);
pb=pi*vars(4)/180; Kp=K*rb*cos(pb);
if key==2, Ti=-Tc/(2*pi*tan(pb));
elseif key==3|key==4, Ti=Tc*(1+sin(pb))/(pi*cos(pb)); Td=Ti/4; end
end
[Gc,H]=writepid(Kp,Ti,Td,N,key);
xlabel('Time')
ylabel('TXPower in dB')