Why my plot doesn't show the line?

clc;
close all;
%common parameters
f=3.5;      %Frequency band [GHz]
pt=40;      %transmitter power[dBm]
pr=27;      %Receiver power[dBm]
n=6;        %Noise figure [dBm] 
ht=5;       %Transmitter antenna height(km) 
hr=0.001;   %Receiver antenna height(km) 
Amn=20;     %The median attenuation relative to free space
gt=17;      %Transmitter Antenna Gain [dBi]
gr_s=15;     %Receiver Antenna Gain [dBi] (stations) 
gr_h=2;      %Receiver Antenna Gain [dBi] (handset)
B=10;        %Bandwidth [MHz]
L=0.3;       %Connector loss [dB]
r=0:5:50;


%Data from user
area_type =input ('Enter type of city (1 - urban, 2 - suburban, 3 - rural):','s');
distance=input('Enter the distance is :','s');
d= str2double(distance);

      
% Okumura Propagation Model
Ght=20*log(ht/200);     %Transmitter Antenna Height Gain Factor 
if(hr<3)                %Reciver Antenna Height Gain Factor
    Ghr=20*log(hr/3);
else
    Ghr=10*log(hr/3);
end
Lf=32.44+20*log10(f)+20*log10(d);   %Free Space Propagation Loss

switch area_type
    case 'urban'
        Garea=13;
    case 'suburban'
        Garea=29;
    case 'rural'
        Garea=35;
end
L50=Lf+Amn-Ght-Ghr-Garea;
Rss_1= pt+gt+gr_s-L50-L;
SNIR= Rss_1/n+1;
c=B*log(1+SNIR);
disp('Propagation pathloss is : ');
disp(L50);

plot(r,L50);
title('Okumura Model Analysis');
xlabel(' distance (Km)');
ylabel('Propagation Path loss(dB) at 50 Km');

Answer 1

[Walter Roberson]

You define a vector r but do not use it. Your calculations are only on scalars. plot() of a scalar never creates a line.

[Shahd Altalhi]

clc;
close all;
%common parameters
f=3.5;      %Frequency band [GHz]
pt=40;      %transmitter power[dBm]
pr=27;      %Receiver power[dBm]
n=6;        %Noise figure [dBm] 
ht=5;       %Transmitter antenna height(km) 
hr=0.01;   %Receiver antenna height(km) 
Amn=20;     %The median attenuation relative to free space
gt=17;      %Transmitter Antenna Gain [dBi]
gr_s=15;     %Receiver Antenna Gain [dBi] (stations) 
gr_h=2;      %Receiver Antenna Gain [dBi] (handset)
B=10;        %Bandwidth [MHz]
L=0.3;       %Connector loss [dB]

%Data from user
area_type =input ('Enter type of city (1 - urban, 2 - suburban, 3 - rural):','s');
distance=input('Enter the distance is :','s');
d= str2double(distance);

      
% Okumura Propagation Model
Ght=20*log(ht/200);     %Transmitter Antenna Height Gain Factor 
if(hr<3)                %Reciver Antenna Height Gain Factor
    Ghr=20*log(hr/3);
else
    Ghr=10*log(hr/3);
end
Lf=32.44+20*log10(f)+20*log10(d);   %Free Space Propagation Loss

switch area_type
    case 'urban'
        Garea=13;
    case 'suburban'
        Garea=29;
    case 'rural'
        Garea=35;
end
L50=Lf+Amn-Ght-Ghr-Garea;
Rss_1= pt+gt+gr_s-L50-L;
SNIR= Rss_1/n+1;
c=B*log(1+SNIR);
disp('Propagation pathloss is : ');
disp(L50);

x=0:5:50;
y=L50;
plot(x,y,'LineWidth',1.5);
title('Okumura Model Analysis');
xlabel(' distance (Km)');
ylabel('Propagation Path loss(dB) at 50 Km');

it also doesn't show

[Walter Roberson]

Change

plot(x,y,'LineWidth',1.5);

to

plot(x,y,'*','LineWidth',1.5);