Plotting multiple lines within a FOR loopin MATLAB

Question

Okay so this sounds easy but no matter how many times I have tried I still cannot get it to plot correctly. I need only 3 lines on the same graph however still have an issue with it.

iO = 2.0e-6;
k = 1.38e-23;
q = 1.602e-19;


for temp_f = [75 100 125]
    T = ((5/9)*temp_f-32)+273.15;
        vd = -1.0:0.01:0.6;
        Id = iO*(exp((q*vd)/(k*T))-1);
        plot(vd,Id,'r',vd,Id,'y',vd,Id,'g');
        legend('amps at 75 F', 'amps at 100 F','amps at 125 F');    

end;       

ylabel('Amps');
xlabel('Volts');
title('Current through diode');

Now I know the plot function that is currently in their isn't working and that some kind of variable needs setup like (vd,Id1,'r',vd,Id2,'y',vd,Id3,'g'); however I really can't grasp the concept of changing it and am seeking help.

Greg G. · Accepted Answer · 2012-04-30 03:57:20Z

3

You can use the "hold on" function to make it so each plot command plots on the same window as the last.

It would be better to skip the for loop and just do this all in one step though.

iO = 2.0e-6; 
k = 1.38e-23; 
q = 1.602e-19; 

temp_f = [75 100 125];
T = ((5/9)*temp_f-32)+273.15;

vd = -1.0:0.01:0.6;
% Convert this 1xlength(vd) vector to a 3xlength(vd) vector by copying it down two rows.
vd = repmat(vd,3,1);

% Convert this 1x3 array to a 3x1 array.
T=T';
% and then copy it accross to length(vd) so each row is all the same value from the original T
T=repmat(T,1,length(vd));

%Now we can calculate Id all at once.
Id = iO*(exp((q*vd)./(k*T))-1);

%Then plot each row of the Id matrix as a seperate line. Id(1,:) means 1st row, all columns.
plot(vd,Id(1,:),'r',vd,Id(2,:),'y',vd,Id(3,:),'g');
ylabel('Amps'); 
xlabel('Volts'); 
title('Current through diode');

And that should get what you want.

answered Apr 30, 2012 at 3:57

Greg G.

311 bronze badge

Sign up to request clarification or add additional context in comments.

1 Comment

user1364968 Over a year ago

The issue is tho I have to use a for loop for the problem, still in basic programming nothing to complicated. whould the plotting method shown above work?

Collectives™ on Stack Overflow

Plotting multiple lines within a FOR loopin MATLAB

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related