Error using plot Vectors must be the same length. [line 29 ERROR]

function moleFractionA = antonie2molfraction(A,B,T,P);
A = [6.80896, 935.86, 238.73]; %1x3 array A is n-butane  
B = [6.87024, 1168.72, 224.21]; %1x3 array B is n-hexane
T = [0:10:1000]; %celsius
P = 1125.09; %torr ~ 1.5 bar
PvaporA = zeros(1,11);
PvaporB = zeros(1,11);
liquidmoleFractionA = zeros(1,11);
vapormoleFractionA = zeros(1,11);
for i = 1:11
    PvaporA(i) = 10 ^ (A(1)-(A(2)/(A(3)+T(i))));
    PvaporB(i) = 10 ^ (B(1)-(B(2)/(B(3)+T(i))));
    liquidmoleFractionA(i) = (P-PvaporB(i)) ./ (PvaporA(i)-PvaporB(i));
    vapormoleFractionA(i) = PvaporA(i) .* liquidmoleFractionA(i) / P;
end 
plot(liquidmoleFractionA, T)
hold on 
plot(vapormoleFractionA, T)
hold off 
xlabel('Mole Fraction of N-Butane')
ylabel('Temperature in Celsius')
title('N-Butane / N-Hexane TXY Diagram')
end

[Torsten]

PvaporA(i) = 10 ^ (A(1)-(A(2)/(A(3)+T(i))));
PvaporB(i) = 10 ^ (B(1)-(B(2)/(B(3)+T(i))));

And you are sure the temperature is in degreeC and the vapor pressure calculated is in torr ?

Answer 1

[Jim Riggs]

The two arguments to the 'plot' command must be the same size, e.g. 'liquidmoleFractionA' must have the same length as 'T'.

A good way to do this is to use the 'T' vector length to define the loop parameter;

npt = length(T)

PvaporA = zeros(1,npt);

... etc.

for i=1:npt

PvaporA(i) = 10 ^ (A(1)-(A(2)/(A(3)+T(i))));

... etc.

Now you simply define the vector 'T', and all of your other vectors will conform to it.