0 个投票

So I have a code and want to plot a couple of features. Long story short, my plot legend is a little confused as to its labels. How can I correct this?
clear;clc;
%inputs
d=5; %feet
h=10; %feet
yi=7; %feet
ysp=5; %feet
dt=30; %seconds
band=1; %feet
%givens
Vimax=100; %gallons per minute
Vimax=Vimax*0.002228; %ft^3/s
aTank=(pi*d^2)/4; %ft^2
tmax=3000;
uL=ysp+band/2;
lL=ysp-band/2;
%valve position
if yi>uL
vp=0;
elseif yi<lL
vp=1;
else
vp=0;
end
t=0;
y=yi;
n=1;
while t(n)<=tmax
%net flow rate
nfl=Vimax*vp-Vout(t); %ft^3/s
%net volume change for a time step
vc=nfl*dt; %ft^3
%determine change in water level
dy=vc/aTank; %feet
y(n+1)=y(n)+dy;
t(n+1)=t(n)+dt;
%next
if y(n+1)>uL
vp=0;
elseif y(n+1)<lL
vp=1;
else
vp=vp;
%vp=-(y(n+1)-ysp)/band+0.5; %CHANGE TO PROPORTIONAL
end
n=n+1;
end
plot(t,y,'r')
hold on
plot(t,ysp,'g+')
plot(t,uL,'bo')
plot(t,lL,'y.')
xlabel('Time in Seconds')
ylabel('Water Level in Feet')
legend('Water Level','Setpoint','Upper Level','Lower Level')

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 采纳的回答

Adam Danz
Adam Danz 2018-6-27
编辑：Adam Danz 2018-6-27

4 个投票

The reason your legend has duplicate symbols is because there are multiple elements plotted for each marker. This is one of the reasons why you should used handles when you call legend().
Replace the plotting section after the while loop with this.
h1 = plot(t,y,'r');
hold on
h2 = plot(t,ysp,'g+');
h3 = plot(t,uL,'bo');
h4 = plot(t,lL,'y.');
xlabel('Time in Seconds')
ylabel('Water Level in Feet')
legend([h1,h2(1),h3(1),h4(1)], 'Water Level','Setpoint','Upper Level','Lower Level')
By the way, I couldn't run your code because the value of 'Vout' is unknown.

2 个评论
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Bailey Smith
Bailey Smith 2018-6-27
I have a function that's called into the code. I totally forgot about that. My bad. And thank you so much for the help!
Parasram Siewlal
Parasram Siewlal 2019-10-15
Thanks, I ran into the same problem and your solution helped.

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更多回答（1 个）

Rik
Rik 2018-6-27

1 个投票

You can use the output of the plot function to get the handles to the objects. Then you can use the list as an input to legend.
temp=plot(t,y,'r');
plothandles=temp(1);
hold on
temp=plot(t,ysp,'g+');
plothandles(2)=temp(1);
temp=plot(t,uL,'bo');
plothandles(3)=temp(1);
temp=plot(t,lL,'y.');
plothandles(4)=temp(1);
xlabel('Time in Seconds')
ylabel('Water Level in Feet')
legend(plothandles,{'Water Level','Setpoint','Upper Level','Lower Level'})

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