How do I create a semicircular live RADAR plot?

I use an ultrasonic sensor mounted on a servomotor to obtain the distance from objects around it.

I use the code attached to use the serial data (through Arduino) and plot a live RADAR. The catch is that I'm trying to design a plot that has an arm that moves back and forth in sync with the servomotor and then darken the area beneath the distance measured to produce the Radar effect.

Code:-

clc;
clear all;
%Customize graph
figure('units','normalized','outerposition',[0 0 1 1]);
whitebg('black');
%Draw Scale Data
th = linspace(0,pi,1000);
R = 10:10:50;  
for i=1:length(R);
x = R(i)*cos(th);
y = R(i)*sin(th);
plot(x,y,'Color', [0.603922 , 0.803922 , 0.196078] ,'LineWidth',1);
hold on;
end
%Draw Axis data
x0 = [0 100 0 0 0 0 ]; 
x1 = [0 100 86.60 50 -50 -86.60]; 
y0 = [0 0 0 0 0 0]; 
y1 = [100 0 50 86.60 86.60 50];
for i=1:length(x0);
hold on;
plot([x0(i),x1(i)],[y0(i),y1(i)] ,'Color', [0.603922 , 0.803922 , 0.196078],'LineWidth',2);
end
h=zeros(100,100);
%Draw Sonar default data
for i=1:180 
hold on;
[x, y] = pol2cart(i*0.0174532925, 100);
h(i) = plot([0,x],[0,y],'g','LineWidth',1);
 hold on;
end;
%define serial port
s1 =serial('COM4');             
s1.BaudRate=9600;                               
fopen(s1);
%Draw Sonar Data
while(1)
data = fgets(s1);
[th, r] = strtok(data);
th= real(str2double(th));
r = str2double(r);
set(th,'color',r);
[x0, y0] = pol2cart(th*0.0174532925, 100);
[x, y] = pol2cart(th*0.0174532925, r);
set(h(th),'String','XData',[x0,x]);
set(h(th),'String',[y0,y]);
m = plot([0,x0],[0,y0],'g','LineWidth',3);
drawnow;
delete(m);
end;
fclose(s1);

I get an error in the line set(th,'color',r);

Answer 1

[othmane kribia]

just try this: set(h(th),'color','r');