plot highest sidelobe level from the beampattern

Angle=0*(pi/180);%angle of interest     
D=500;%distance between ref. node and destination.
x1=600;%ref. node value.
y1=400;%ref. node value.
xd=x1+(D*cos(Angle)); %destination value.
yd=y1+(D*sin(Angle)); %destination value.
N=100;%number of elements.
freq=3e9;
c=3e8;
lambda=c/freq;
d_s=.1*lambda%inter-element spacing between sensor.

for n=1:N
x(n)=(x1+(n*(d_s)));%x axes value for N elements.
z(n)=y1;%y axes value for N elements.
d(n)= sqrt((yd-y1)^2+(xd-x(n))^2);%distance between destination and sensor.
t(n)= ((2*pi)/lambda)*(d(1)-d(n));%phase lag corresponding to the reference node.
c(n)=exp(-i*t(n));%weight 

count=0;
for angle=0:360
 count=count+1;
Xd=x1+(D*cos(angle*pi/180));
Yd=y1+(D*sin(angle*pi/180));
d1(n,count)= sqrt((Yd-y1)^2+(Xd-x(n))^2);
%d1(n,count)=sqrt(((y1+(D*sin(angle*pi/180)))-y1)^2 + (x1+(D*cos(angle*pi/180))-(x1+(n*(d_s))))^2);%distance between destination and sensor
k(n,count)=((2*pi)/lambda)*(d1(n,count)); %phase lag for each sensor.
y(n,count)=(exp(-i*k(n,count))*c(n)); %weight multiplication to correct the phase lag.

end
end

Y=sum(y);
YY=abs(Y);
figure(3);
plot(YY)

this is my code to plot the beampattern of an uniform array...now using the beampattern produced, i need to obtain the highest sidelobe level and plot it in a different graph. how do i do this?