Why is this wrong??

Hello :) I'm trying to draw the plots for E=a*c when j = 1 and E = a*b when j assumes other values, all in the same figure. The program just draws the first one, for E=a*c, and I cant understand why because it computes all different E for all the j (computes but does not do the plot). Can you tell me what I'm doing wrong? Your help will be very appreciated! Thanks in advance!

hold on
for j = 1:i

   tau = (12*v*t(j)*Myr)/ro^2;
   I = besseli(0.25,2*x./tau);

   a = (md/(2*pi*ro));
   b = (tau^-1).*(x.^-1/4).*I.*exp(-(1+x.^2)/tau);
   c = normpdf(x,1,0.05);

   if j == 1
       E = a.*c;
   else 
       E = a.*b 
   end
   plot(x, E.*(1/a), colors(j))
end
hold off

[Matt J]

The posted code doesn't run, since you haven't defined 'i' for us, and other variables as well.

[Iris]

    Ms = 1.98919e33;
Rs = 6.9599e10;
Myr = 3.15569e13;
v = 1e5;
md = 0.01*Ms;
ro = 2*Rs;
x = [0:0.016:16] 
t = [0:2e12:1e13];
i = length(t);
colors = ['r' 'b' 'g' 'b' 'g' 'b' ];

for j = 1:i

   tau = (12*v*t(j)*Myr)/ro^2;

   I = besseli(0.25,2*x./tau);

   a = (md/(2*pi*ro));
   b = (tau^-1).*(x.^-1/4).*I.*exp(-(1+x.^2)/tau);
   c = normpdf(x,1,0.05);

   if j == 1
       E = a.*c;
   else 
       E = a.*b 
   end

   hold on
   plot(x, E.*(1/a), colors(j))
end
hold off

end

[Christoph]

Weird since it works for me (R2008a, V7.6.0). Have you checked the output using subplot(2,3,j) at the start of the loop? since the value of E peaks at "8" in the 1st and <10^-12 in the other plots, so all together they appear as line... Otherwise, which Matlab release do you use?

Answer 1

[Matt Fig]

I run your code and it plots 6 lines. check for yourself:

>> length(findobj('type','line'))

ans =

       6

I think maybe you are not noticing because some lines overlap. Have a look:

ylim([0 1e-12])

Answer 2

[Matt J]

Might be useful to change this

   hold on
   plot(x, E.*(1/a), colors(j))

to this

semilogy(x, E.*(1/a), colors(j));
 hold on