MATLAB ploting graph incorrectly, different from same code in Python.

I'm beggining to learn MATLAB.

I got the following code, but the graph doesn't match the data points when putting the P values manually.

%Pressure
P = 0:1/100:14;

%Parameters Pb
C = 0.55;
alpha = 28.9;
Ba = 0.44;
B = 43.7;
T = 300;
Vr = (1-3*C*alpha*(300-T))*(((P*Ba/B)+1).^-(1/Ba));

K = 2091*(Vr).^0.87;
Theta = 86*((Vr).^-((2.629*(Vr).^(1.2))));

%Resistivity
r = (K*T/(4*(Theta).^2))*(1-(1/18)*(Theta/T).^2+(1/480)*(Theta/T).^4);
r0 = (2091*T/(4*(86).^2))*(1-(1/18)*(86/T).^2+(1/480)*(86/T).^4);

plot(P,r/r0)

I wrote the same code for python and it ploted correctly

from pylab import plot, show, xlabel, ylabel, title
from numpy import linspace


#Pressure
P = linspace(0, 14, 100)

#Parameters Pb
C = 0.55
alpha = 28.9
Ba = 0.44
B = 43.7
T = 300
Vr = (1-3*C*alpha*(300-T))*(((P*Ba/B)+1)**-(1/Ba))

K = 2091*(Vr)**0.87
Theta = 86*((Vr)**-((2.629*(Vr)**(1.2))))

#Resistivity
r = (K*T/(4*(Theta)**2))*(1-(1/18)*(Theta/T)**2+(1/480)*(Theta/T)**4)
r0 = (2091*T/(4*(86)**2))*(1-(1/18)*(86/T)**2+(1/480)*(86/T)**4)

plot(P, r/r0)
xlabel('P(GPa)')
ylabel('R(P)/R(P0)')
title('Pb')
show()

What is wrong with my MATLAB code?

Answer 1

[the cyclist]

In your definition of r, you missed a couple spots that required array operations instead of matrix operations:

%Pressure
P = 0:1/100:14;
P0 = 0.000101325;

%Parameters Pb
C = 0.55;
alpha = 28.9;
Ba = 0.44;
B = 43.7;
T = 300;
Vr = (1-3*C*alpha*(300-T))*(((P*Ba/B)+1).^-(1/Ba));

K = 2091*(Vr).^0.87;
Theta = 86*((Vr).^-((2.629*(Vr).^(1.2))));

%Resistivity
r = (K*T./(4*(Theta).^2)).*(1-(1/18).*(Theta/T).^2+(1/480).*(Theta/T).^4);
r0 = (2091*T/(4*(86).^2))*(1-(1/18)*(86/T).^2+(1/480)*(86/T).^4);

plot(P,r/r0)