MATLAB: Matrix Dimensions must agree

MATLABmatrix

FUNCTION:
function P = preos_P(V, T, Pc, Tc, w)
R = 8.314;
Tr = T./Tc;
a = 0.4572355289.*(R.^2.*T.^2./Pc);
b = 0.0777960739*(R.*Tc./Pc);
k= 0.37464+1.54226.*w-0.26992.*w.^2;
alpha = (1+k.*(1-Tr.^1/2)).^2;
P = (R.*T./(V-b))-(alpha.*a)/(V.^2+2.*b.*V-b.^2);
end
% takes inputs of temperature (T ), volume (V ), critical pressure (Pc),
% critical temperature (Tc), and acentric factor (w) and returns the pressure.
SCRIPT:
% takes inputs of temperature (T ), volume (V ), critical pressure (Pc),
% critical temperature (Tc), and acentric factor (w)
% and returns the pressure.
clear; clc
T = linspace(273, 373, 100)'; %Temperature in K
Tc = [304.2 190.6 419.6];
Pc = [7.382 4.604 4.02];
w = [0.228 0.011 0,187];
V = .1*1000;
R = 8.314;
P = preos_P (V, T, Pc, Tc, w);
Ps = P;
Ts = T;
plot(Ts,Ps)
legend('carbon dioxide', 'methane', '1-butene', 'Location', 'NorthWest')
title ('[ressures of gases')

Best Answer

  • T has 100 elements whereas Tc has only 3 (reason for the error) , both should have same number of elements
T./Tc % here
  • Matlab interprets that w has 4 elements 
w = [0.228 0.011 0,187];
               %  ^----- has to be a dot
If all the above statements are fulfilled plot can be expected.
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