Help with for loop

Need to display the two graphs in the question. I am having a hard time with the for loop.

Answer 1

[Walter Roberson]

You have a for i loop 1 to the number of elements in X

Inside that loop you have

for i=1,2;

Notice that you are reusing the variable name i, interfering with i from the outer loop.

Notice that you used 1,2 not 1:2

[Angelina Encinias]

Okay it also says invalid expression for Line 16

[Walter Roberson]

Y=(x(i)*L(i)*(P(i))/P
  1 2 1  2 1 2 3 21

You have one more ( than you have )

You also have a complete vector on the right side of the / operator. The / is very unlikely to be the operation you are thinking it is. A/B is similar to innerProduct(A, pinv(B))

What size are you expecting Y to come out as?

You are overwriting all of Y in each iteration.

[Angelina Encinias]

Okay makes sense how do I fix the loop?

[Torsten]

Getting P from x1 (thus the liquid line of the first graph) should be no problem (can you write down the formula ?).

Thus getting y1 from x1 should also be no problem (second graph) (can you write down the formula ?).

The only thing for which you have to use "fzero" is to get P from y1 (vapour line of the first graph) (can you write down the equation you have to solve ?).

[Angelina Encinias]

The equations are in the question. I wrote down the equations in the code. Is there an error for how I wrote them?

[Torsten]

Is there an error for how I wrote them?

Yes, e.g. it makes no sense trying to find a zero of the equation defined in "fun".

Don't start coding before you have a strategy how to get the result.

I suggest you try to answer the three questions (here or for yourself).

Once you have the answers, coding will be simple.

This may sound arrogant and educational, but it's the truth.

[Angelina Encinias]

Heres my edited code but nothing is showing on the figures?

[Torsten]

a = 1.4106;
b = 1.3438;
Pvap1 = 1.1541;
Pvap2 = 0.7609; 

gamma1 = @(x1) exp(a./(1+(a/b)*x1./(1-x1)).^2);
gamma2 = @(x2) exp(b./(1+(b/a)*x2./(1-x2)).^2);

x1 = 0:0.01:1;
x2 = 1 - x1;
P = x1.*gamma1(x1)*Pvap1 + x2.*gamma2(x2)*Pvap2;
y1 = x1.*gamma1(x1)*Pvap1./P;

figure(1)
plot(x1,P)
hold on
plot(y1,P)
figure(2)
plot(x1,y1)