MATLAB: There is no line in the graph

graph

clc;
disp('==========================================================================================');
disp('=                                                                                        =');
disp('=                       PROGRAM PERANCANGAN TANGKI PENGADUK (MIXING)                     =');
disp('=                                                                                        =');
disp('==========================================================================================');
disp('');
disp('');
disp('                             ===============================');
disp('                             =     Pilih Jenis Larutan     =');
disp('                             ===============================');
disp('=====================');
disp('=1. Larutan NaCl    =');
disp('=2. Larutan C6H12O6 =');
disp('=====================');
pil=input ('Masukkan Pilihan larutan= ');
clc;
switch pil
    case 1
        disp('                             ===================================');
        disp('                             =           Larutan NaCl          =');
        disp('                             ===================================');
        n=input ('Masukkan kecepatan pengaduk (rps)= ');
        d=input ('Masukkan diameter pengaduk (m)= ');
        disp('==========================================================================================');
        disp(' Densitas    Kec. Pengaduk    Diameter Pengaduk    Viskositas      NRe       Jenis Aliran ');
        disp(' (Kg/m^3)       (Rps)                (m)            (Kg/Ms)                               ');
        disp('==========================================================================================');
        for a=n:2:10;        
        den=2160;
        vis=0.94;
        nre=(den*a*d)/vis;
        if nre<2000
        c='ALIRAN LAMINER';
    elseif nre>2000 & nre<4000
        c='ALIRAN TRANSISI';
    else
        c='ALIRAN TURBULEN';
    end;
fprintf('%8.2f%13.2f%19.2f%18.2f%14.2f%18s\n',den,a,d,vis,nre,c);
        end;
        disp('');
        disp('');
        disp('                               ===================================');
        disp('                               =     Menghitung Power Tangki     =');
        disp('                               ===================================');
        p=input ('Input power (watt)= ');
        disp('');
        disp('=============================================================================================================');
        disp(' Power     Kec. Pengaduk    Diameter Pengaduk    Densitas    Konstanta Gravitasi     NRe        power Number ');
        disp('(Watt)         (Rps)               (m)           (Kg/m^3)        (Kg.m/N.S^2)                   (Kg.m^2/S^2) ');
        disp('=============================================================================================================');
        while n<=10
        g=1;
        Np=(n.^3*d.^3*den)/p*g;
        fprintf('%8.2f%13.2f%19.2f%18.2f%14.2f%19.2f%18.2f\n',p,n,d,den,g,nre,Np);
        n=n+2;
        plot(Np,nre,'--r*','linewidth',2,'markeredgecolor','g');
        hold on;
        grid on;
        set(gca,'fontsize',12);
        title('Grafik Hubungan Nre Vs Power Number','fontweight','bold','fontsize',12);
        xlabel('Power Number (Kg.m^2/S^2)');
        ylabel('Nre');
        end;
end;

Best Answer

"Why there is no line in my graph?"
Because you are plotting one scalar point on each loop iteration. This will NOT give a line:
for k = 1:10
    plot(k,sqrt(k),'-*') % indivdual points does NOT plot a line!
end
If you want to plot a line, then you will need to store those scalar values in vectors, and plot the vectors after the loop. To plot lines you need to do something like this:
X = 1:10
Y = sqrt(X);
plot(X,Y,'-*') % plotting with vectors gives a line!
So basically before your loop you should preallocate some vectors, then inside the loop store your output values in the vectors, and then after the loop you plot the vectors.
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