multiple graphs plotting error

ro=10;

ri=30;

t=0:0.1:2000;

ci=0.5

c_L=(ci*ri)/ro.*(1-exp(1).^((-ro.*t./((ri-ro).*t+1500))));

plot(t,c_L)

hold on

ro=15;

ri=25;

c_L=(ci*ri)/ro.*(1-exp(1).^((-ro.*t./((ri-ro).*t+1500))));

plot(t,c_L)

ro=25;

ri=15;

c_L=(ci*ri)/ro.*(1-exp(1).^((-ro.*t./((ri-ro).*t+1500))));

plot(t,c_L)

For the interval t it should be 0 to 2000, but when I run MATLAB with that interval graph looks very weired

However, with interval 0 to 100 looks fine.

What should I do?

Answer 1

[Star Strider]

The ‘t’ vector for the first series of curves is:

t=0:0.1:100; 

and for the second:

t=0:0.1:2000; 

That likely explains the difference.

To plot ‘t’ from 0 to 2000, define ‘t’ over the desired range.

[Jong Hyun Lee]

My question was for first series t interval should be 0 to 2000 but when I run it (with 0 to 2000) graph looks very weired. But with interval 0 to 100 looks fine.

[Star Strider]

The problem is in the third plot of your original (unedited Question — I saved the previous code), specifically:

ro=25;
ri=15;
c_L=(ci*ri)/ro.*(1-exp((-ro.*t./((ri-ro).*t+1500)))); 
plot(t,c_L)

In the previous plots, (ro < ri) so the difference (ri-ro) was positive and the code gave you the result you want. With (ro > ri), the exponent becomes positive, and when ‘t’ is 150.6, ‘c_L’ is . I have no idea what you are calculating here, however so long as you should get the sort of result you want.

[Jong Hyun Lee]

that means i cant draw graph for ro>ri?

[Star Strider]

You certainly can draw it. You just need to be prepared for results that may not be what you want. Or alternatively, use ylim to restrict the display to only positive values of ‘c_L’.

[Jong Hyun Lee]

i see, thanks!

[Star Strider]

As always, my pleasure!