plotting multiple line graphs in one plot

Hey. I was writing a code to show efficiency of thermoelectric generators in one plot. tc is constant in each statement, first z changes and for each z, I want to plot a line based on the th variation. each line, for instance, z=0.5 and th from 300 to 1250 has a specific color for readability.

tc(1:20)=298;th=300:50:1250;figure;hold on;
for t=1:20
    z(t)=t./4;
for i=1:20

    etha(i)=((th(i)-tc(i))./th(i)).*((sqrt(1+((z(t).*th(i)+tc(i))./2))-1)./...
        ((sqrt(1+((z(t).*th(i)+tc(i))./2))-(tc(i)/th(i)))));

ln=plot(th(i),etha(i));
ln.Color=(1./t).*[1 1 1];
ln.LineWidth=2;
ln.Marker='*';
end

end
hold off

the output is like this

but I desire for an output like this

anyone has any suggestion? I know I'm amateur....

Answer 1

[David Fletcher]

Might need some more tinkering - this is limited to 7 lines rather than the 20 you have in your code

tc(1:20)=298;
th=300:50:1250;

for t=1:7
    z(t)=t./4;
for i=1:20
    etha(t,i)=((th(i)-tc(i))./th(i)).*((sqrt(1+((z(t).*th(i)+tc(i))./2))-1)./...
        ((sqrt(1+((z(t).*th(i)+tc(i))./2))-(tc(i)/th(i)))));

end
end

ln=plot(th,etha,'*-','LineWidth',2);

[Hesam Jokar]

Thanks. This resolved my issue.