why wont my code show my line in the plot?

Question

ALEX MC QUAID 2020-11-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/651473-why-wont-my-code-show-my-line-in-the-plot

编辑： Adam Danz 2020-11-17

r=1.1;c=1.2;po=80.;qo=700.;
rqo=r*qo;rc=r*c;
t1=linspace(0.,0.2,10);
t2=linspace(0.2,0.8,10);
p1=(qo/c*((rc*exp(t1/rc)-rc)-5.0.*...
    (t1*rc.*exp(t1/rc)-rc^2.0*(exp(t1/rc-1.)))+po).*exp(-t1/rc))
p2=(qo/c*((rc*exp(0.2/rc)-rc)-5.0.*...
    (0.2*rc.*exp(0.2/rc)-rc^2.0*(exp(0.2/rc-1.)))+po).*exp(-t2/rc))
figure(1);
plot(t1,p1,t2,p2);
ylabel('Pressure (mmHg)'); xlabel('Time (s)');
axis([0 0.8 1 130]);

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Answer 1

Adam Danz 2020-11-17

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https://ww2.mathworks.cn/matlabcentral/answers/651473-why-wont-my-code-show-my-line-in-the-plot#answer_547833

编辑：Adam Danz 2020-11-17

The code works well if you remove the last line. Note that y-limit of your plot is 25000-50000. The last line of your code is setting the ylim to [1,130] which doesn't show any of the data.

Perhaps you're looking for

axis tight

r=1.1;

c=1.2;

po=80.;

qo=700.;

rqo=r*qo;

rc=r*c;

t1=linspace(0.,0.2,10);

t2=linspace(0.2,0.8,10);

p1=(qo/c*((rc*exp(t1/rc)-rc)-5.0.*...

(t1*rc.*exp(t1/rc)-rc^2.0*(exp(t1/rc-1.)))+po).*exp(-t1/rc));

p2=(qo/c*((rc*exp(0.2/rc)-rc)-5.0.*...

(0.2*rc.*exp(0.2/rc)-rc^2.0*(exp(0.2/rc-1.)))+po).*exp(-t2/rc));

figure(1);

plot(t1,p1,t2,p2);

ylabel('Pressure (mmHg)'); xlabel('Time (s)');

●

ylim(gca)

ans = 1×2

25000 50000

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ALEX MC QUAID 2020-11-17

the pressure values are supposed to be between 1 and 130 does this mean my calculations are wrong?

Adam Danz 2020-11-17

编辑：Adam Danz 2020-11-17

Yes, unless the difference can be explained by a unit-conversion.

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Answer 2

Setsuna Yuuki. 2020-11-17

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/651473-why-wont-my-code-show-my-line-in-the-plot#answer_547838

编辑：Setsuna Yuuki. 2020-11-17

you should change the last line

r=1.1;c=1.2;po=80.;qo=700.;
rqo=r*qo;rc=r*c;
t1=linspace(0.,0.2,10);
t2=linspace(0.2,0.8,10);
p1=(qo/c*((rc*exp(t1/rc)-rc)-5.0.*...
    (t1*rc.*exp(t1/rc)-rc^2.0*(exp(t1/rc-1.)))+po).*exp(-t1/rc))
p2=(qo/c*((rc*exp(0.2/rc)-rc)-5.0.*...
    (0.2*rc.*exp(0.2/rc)-rc^2.0*(exp(0.2/rc-1.)))+po).*exp(-t2/rc))
figure
plot(t1,p1,t2,p2);
ylabel('Pressure (mmHg)'); xlabel('Time (s)');
axis([0 0.8 1 50000]); % before: axis([0 0.8 1 130]); 