MATLAB Answers

Plots with different colors

2 ビュー (過去 30 日間)
Yen Tien Yap
Yen Tien Yap 2021 年 8 月 25 日
編集済み: Simon Chan 2021 年 8 月 25 日
Hi, I want to create the scatter plot with three different colours represents three different regions. I think something wrong with the for loop, can someone help me with that? Thank you.
rho=1000; %[kg/m3]
D=12.6*10^-3; %[m]
L=1.5; %[m]
miu=0.001; %[Pas]
g=9.81;
A=pi*D^2/4;
Q0=[1600,1500,1400,1300,1200,1100,1000,900,800,700,600,500,400,300,240,220,...
200,180,160,140,120,100,80,70,70,60,50,40,30,20,10];%[L/hr]
Q=Q0/(1000*3600);
%Wet-wet digital gauge
P_dpg=[20.1,17.5,15.7,13.1,11.6,9.3,8,6.5,5.3,4.1,3,2.1,1.3,0.8]; %[kPa]
%Inverted manometer
h=[6.9,5.9,5,4.1,3.2,2.6,1.8,1.3,0.7,0.5]; %[cm]
h_m=h/100;
P_mtr=rho*g*h_m;
%Capsuhelic gauge
P_cpg=[33,31,28,23,17,12,8];
P=[P_dpg.*1000,P_mtr,P_cpg];
V=Q/A;
Re=rho*V*D/miu;
f=P*D./(2*rho*L*V.^2);
X=Re(25:31);
Y=f(25:31);
p=polyfit(log(X),log(Y),1)
p = 1×2
-1.2271 4.1752
y=polyval(p,log(X));
figure(1)
for i=1:length(Re)
if Re(i) < 2*10^3
loglog(Re,f,'xb','LineWidth',1)
elseif Re(i)>=2*10^3 & Re(i)<=3*10^3
loglog(Re,f,'xr','LineWidth',1)
else
loglog(Re,f,'xg','LineWidth',1)
end
end
hold on
loglog(X,exp(y),'--r','LineWidth',1.5)
grid on
xlim([10^2 10^5])
ylim([0.001 0.1])
xlabel('Reynolds number Re')
ylabel('Friction factor f')
title('f vs Re')

採用された回答

Simon Chan
Simon Chan 2021 年 8 月 25 日
Put the index and hold on inside the loop
figure(1)
for i=1:length(Re)
if Re(i) < 2*10^3
loglog(Re(i),f(i),'xb','LineWidth',1)
hold on
elseif Re(i)>=2*10^3 & Re(i)<=3*10^3
loglog(Re(i),f(i),'xr','LineWidth',1)
hold on
else
loglog(Re(i),f(i),'xg','LineWidth',1)
hold on
end
end
  3 件のコメント
Simon Chan
Simon Chan 2021 年 8 月 25 日
It is better to separate the data into 3 groups since the plot was performed point by points and hence there were actually 31 data and hence the legend above is showing the last 3 points only.
The code needs to be adjusted like the following:
figure(1)
Re_A = Re(Re < 2*10^3); % Group 1
f_A = f(Re < 2*10^3);
Re_B = Re(Re>=2*10^3 & Re<=3*10^3); % Group 2
f_B = f(Re>=2*10^3 & Re<=3*10^3);
Re_C = Re(Re > 3*10^3); % Group 3
f_C = f(Re > 3*10^3);
loglog(Re_A,f_A,'xb','LineWidth',1) % Plot Group 1 data
hold on % In this case, one hold on is enough
loglog(Re_B,f_B,'xr','LineWidth',1) % Plot Group 2 data
loglog(Re_C,f_C,'xg','LineWidth',1) % Plot Group 3 data
legend('Laminal flow', 'Transitional zone', 'Turbulent flow')

サインインしてコメントする。

その他の回答 (0 件)

カテゴリ

タグ

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by