i have a problem connecting 5 dots together using the plot fuction. i should have two parrallel lines but i get a blank sheet

clear,clc,clf

format long

Q=0.03;

rouh=847;

g=9.81;

Gamma=(rouh.*g);

Zs=0;

Ze=0;

L=500;

Ks=(6*10.^-5);

viscosity=(1.1*10.^-6);

V=1.34:0.5:4.5

for I=1

D=sqrt(((4.*Q))./(V.*pi))

end

Re=(V.*D./viscosity);

Er=(1.*10.^-8);

Fo=0.01;

for I=0:1:10^6;

Fn=(1./(-4.*log10((Ks./(3.71.*D))+((1.26)./(Re.*sqrt(Fo)))))).^2;

E=abs((Fn-Fo)/Fn);

if E<=Er;

display(Fn),display(E),break,

end

if E>Er;

Fo=Fn;

end

end

Hloss=((Fn.*L.*Q.^2)./(12.*D.^5))

Hpump=Hloss

%calculating Hloss every 100M

Hloss=((Fn.*L.*Q.^2)./(12.*D.^5))

Hpump=Hloss

%calculating Hloss every 100M

for HLC=(1:100:500);

r0=HLC

HlossN=((Fn.*HLC.*Q.^2)./(12.*D.^5))

TEL=(Hpump-HlossN+Zs)

r1 = TEL(:,1)

HGL=(TEL-((V.^2)./2.*g))

r2 = HGL(:,1)

plot(r0,r1,'LineStyle', '--')

hold on

plot(r0,r2,'LineStyle', '--')

end

Answer 1

[Cris LaPierre]

You plot command is inside a for-loop that runs 5 times (HLC == 1, 101, 201, 301, 401). Placing it here means it will plot the data one point at a time (not connecting them). Nothing is appearing becaues you have only specified LineStyle and no Marker style. Since no line appears when you plot a single point, the result is you see nothing in the plot. Try changing your plot command to this:

plot(r0,r1,'o','LineStyle', '--')

If you want the plot command to automatically connect the lines, first build a vector with all the numbers and then plot (outside the for loop).

[omar mahallawy]

unfortunatly i already tried the new plot with the linestyle and it only shows me the dots (unconnected)

clear,clc,clf
format long
Q=0.03;
rouh=847;
g=9.81;
Gamma=(rouh.*g);
Zs=0;
Ze=0;
L=500;
Ks=(6*10.^-5);
viscosity=(1.1*10.^-6);
V=1.34:0.5:4.5
for I=1
D=sqrt(((4.*Q))./(V.*pi))
end
Re=(V.*D./viscosity);
Er=(1.*10.^-8);
Fo=0.01;
for I=0:1:10^6;
    Fn=(1./(-4.*log10((Ks./(3.71.*D))+((1.26)./(Re.*sqrt(Fo)))))).^2;
    E=abs((Fn-Fo)/Fn);
    if  E<=Er;
     display(Fn),display(E),break,
      end
if E>Er;
   Fo=Fn;
end
end
Hloss=((Fn.*L.*Q.^2)./(12.*D.^5))
Hpump=Hloss
%calculating Hloss every 100M
Hloss=((Fn.*L.*Q.^2)./(12.*D.^5))
Hpump=Hloss
%calculating Hloss every 100M
 for HLC=(1:100:500);
HlossN=((Fn.*HLC.*Q.^2)./(12.*D.^5))
TEL=(Hpump-HlossN+Zs)
TEL1 = TEL(:,1);
TEL2 = TEL(:,2);
TEL3 = TEL(:,3);
TEL4 = TEL(:,4);
TEL5 = TEL(:,5);
TEL6 = TEL(:,6);
TEL7 = TEL(:,7);
HGL=(TEL-((V.^2)./2.*g))
HGL1 = HGL(:,1);
HGL2 = HGL(:,2);
HGL3 = HGL(:,3);
HGL4 = HGL(:,4);
HGL5 = HGL(:,5);
HGL6 = HGL(:,6);
HGL7 = HGL(:,7);
subplot(3,3,1)
plot(HLC,TEL1,'+b','LineStyle', '--')
hold on
plot(HLC,HGL1,'+b','LineStyle', '--')
subplot(3,3,2)
plot(HLC,TEL2,'+c','LineStyle', '--')
hold on
plot(HLC,HGL2,'+c','LineStyle', '--')
subplot(3,3,3)
plot(HLC,TEL3,'+m','LineStyle', '--')
hold on
plot(HLC,HGL3,'+m','LineStyle', '--')
subplot(3,3,4)
plot(HLC,TEL4,'+c','LineStyle', '--')
hold on
plot(HLC,HGL4,'+c','LineStyle', '--')
subplot(3,3,5)
plot(HLC,TEL5,'+k','LineStyle', '--')
hold on
plot(HLC,HGL5,'+k','LineStyle', '--')
subplot(3,3,6)
plot(HLC,TEL6,'+g','LineStyle', '--')
hold on
plot(HLC,HGL6,'+g','LineStyle', '--')
 subplot(3,3,7)
plot(HLC,TEL7,'+r','LineStyle', '--')
hold on
plot(HLC,HGL7,'+r','LineStyle', '--')
 end 

[Jan]

@omar: Cris has answered the question already and explained, that you have to create the vectors at first. See this example:

subplot(1, 2, 1, 'NextPlot', 'add');
for k = 1:10
    plot(k, rand, 'o-');
end

subplot(1, 2, 2, 'NextPlot', 'add');
v = nan(1, 10);
for k = 1:10
    v(k) = rand;
end
plot(1:10, v, 'o-');