Flash function helps to perform the pT flash calculation for alkanes
assuming ideal gas and liquid behaviour.
[a,x,y] = flash(comp,z,p,T)
a = mole fraction of vapour.
x = mole fraction in liquid
y = mole fraction in vapour
z = mole fraction in mixture (make sure that sum(z) = 1)
comp = Cells of strings of the name of the constituents of the gas
p = pressure
T = Temperature
Example.

If we have a mixture of methane, ethane and propane, with mole fractions of
0.3,0.4,0.2 in a mixture and we want to obtain a flash result at T 200k,
pressure of 20bars

We simply define
p = 20;
T = 200;
z = [0.3,0.4,0.2];
comp = {{'methane'},{'ethane'},{'propane'}};

and then call
[a,x,y] = flash(comp,z,p,T)