# how to code equation

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Cesar Cardenas on 3 Feb 2023
Commented: Walter Roberson on 17 Feb 2023
I'm trying to code these equations. This is my attempt. I would like to plot Cf vs x/L, but x/L as I have it shows me an error..the same with delta/x, not sure why? any help will be greatly appreciated. Thanks much. Re = 0:500:1000;
x/L = 0:0.2:1;
Cf = 0.664*(Re)^-0.5;
delta/x = 5.0*(Re)^-0.5;
Les Beckham on 3 Feb 2023
Edited: Les Beckham on 3 Feb 2023
What are x, L, and delta?
Also, you can't put an expression like x/L on the left hand side of an assignment statement, only a variable name (optionally indexed).

Sulaymon Eshkabilov on 3 Feb 2023
Here is the corrected code:
Re = 0:50:1000;
xL = linspace(0,1, numel(Re));
Cf = 0.664*(Re).^(-0.5);
deltaX = 5.0*(Re).^(-0.5);
plot(Cf, xL, 'ro', 'markerfacecolor', 'y')
xlabel('C_f')
ylabel('x_L')
grid on Walter Roberson on 17 Feb 2023
Your h, q, and Re are all scalars, so plotting them on the same graph is not going to be interesting.
T1 = 30;
T2 = 40;
v = 0.5;
x1 = 0.01;
x2 = 0.05;
Pr = 5.18;
nu = 7.708;
k = 0.6184;
d = 995;
Re = v*(x2-x1)/nu
Re = 0.0026
h = 0.3314*(Re.^(0.5))*(Pr.^(0.3))*(k/x2 - x1)
h = 0.3417
q = h*(x2 - x1)*1*(T2-T1)
q = 0.1367
plot([h, q, Re],'r*') 