How to use fsolve when a nonlinear equation given two arrays of parameters (not the variables)? Why can't I use for loop?

I want to find osmotic pressure of a solution as follows. Please let me know how I find y(1) values with varying T and P. Thank you.

T=[303 313 323];

P=0:1:10

function Z=osmotic(y)

%y(1)= pi, osmotic pressure [bar]

Cfb=0.05; %[mol/L]

VHF=2;

z=0.0278; [kg.m-2.s-1]

for k=1:length(T)

for j=1:length(P)

Z(1)=y(1)/(VHF*R*T(k))- Cfb*exp(B(1,k)*(Pv((Tf(k)),P(j))-Pv(Tp(k),y(1)))/z);

end

end

end

%Guess osmotic pressure

VHF=2;

Cfb=0.05;

y0=VHF*R*T*Cfb;

%fsolve initiation for osmotic pressure

options=optimset('display','iter');

pi=fsolve(@osmotic,y0,options);

Answer 1

[Stephan]

Hi,

you could try to vectorize your function in order to avoid for loops - here is a simple example:

% Constant 1 as a row vector
T=[10 20 30];

% Constant 2 as a column vector
P=(1:10)';

% Vectorized function to avoid for loop
fun = @(x,T,P) T .* x - P.^2;

% Preallocate x0 with the size of the resulting matrix
x0 = zeros(numel(P),numel(T));

% call fsolve
sol = fsolve(@(x)fun(x,T,P),x0)

% test solutions
should_be_all_near_or_equal_to_zero = fun(sol,T,P)

[Duong Nguyen]

I think it works for two constants T and P. Thank you!

But if I have more constants, e.g. Tf, Tp, and B in the following code so can you show me how to do it? (B, Tf, Tp depends on T). I appreciate your help