Put multiple loglog plots on one figure

Hello...I am trying to put 3 loglog plots on the same figure but this is not working. Any recommendations or small things I'm missing?

Thanks! :)

clear
clc
close all
format short

Re = 10^4:1000:10^8;

%Bruus
B = @(x) .25*(log((x/3.7)+(5.74./(Re).^.9)));
%Haaland
H = @(x) (1./(-1.8*log((x/3.7)^1.11+(6.9./Re)))).^2;

%Figure 1
eD1 = 0;
B1 = B(eD1);
H1 = H(eD1);
figure;
loglog(Re,B1,'r')
hold on
loglog(Re,H1,'--')
title('f vs. Re e/D = 0');
xlabel('Re');
ylabel('f');
legend('Bruus','Haaland');
grid on

Answer 1

[madhan ravi]

Isn’t this normal? because the domain of the log function starts from 0+ to wards positive infinity that’s why it’s ignoring negative arguments.

[madhan ravi]

There’s nothing wrong with the code because you have used hold on option which is supposed to hold multiple plots in one figure but as i said there’s some malfunctioning in mathematics.

[madhan ravi]

See in your B , log(0/3.7) is exactly the same as log(0) log doesn’t contain zero as it’s domain since it starts from 0+ as mentioned before :)

[madhan ravi]

See http://www.astro.umd.edu/~cychen/MATLAB/Logarithmic_Scaling_Info.html , read the last paragraph in the link.

[Josh Glenn]

okay so it should put them on the same graph? even when the mathematical error is fixed it still only puts one on the log scale graph. Is there something small I'm missing?

[madhan ravi]

It should plot all the graphs if you fix the mathematical error.