MATLAB: Plotting does not work well.

MATLABplotplotting

Code :

———————————

T= 323.15;

A1= 4.01814;

B1= 1203.835;

C1= -53.226;

A2= 4.08245;

B2= 1346.382;

C2= -53.508;

Psat1= 10^(A1-(B1/(T+C1)));

Psat2= 10^(A2-(B2/(T+C2)));

x= [0:0.05:1]

y= ((Psat1)*(x))/((x)*(Psat1)+(1.-x)*(Psat2))

plot(x,y,'r+')

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I want to plot the relationship between x and y. Although y is an expression for x, this code holds y at one value. I want to know what is the problem, and how to change the code to operate it as I intended.

Best Answer

T= 323.15; 
A1= 4.01814;
B1= 1203.835;
C1= -53.226; 
A2= 4.08245;
B2= 1346.382;
C2= -53.508; 
Psat1= 10^(A1-(B1/(T+C1)));
Psat2= 10^(A2-(B2/(T+C2)));
x= [0:0.05:1]
y= ((Psat1).*(x))./((x).*(Psat1)+(1.-x).*(Psat2))
plot(x,y,'r+')

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MATLAB: How to put the results from a while loop in a matrix

Kaicheng - you probably can remove the line

syms x y

since I can't see the y being used in the code, and the x is overridden by the loop step variable. A problem is that you are treating t as if it were an array (at one line of code) and then as a scalar (at another line of code)

for x=0:10
    t=70;                               % <---- here t is a scalar and is being reset on each iteration
    psat1=exp(a1-b1/(t+c1));
    psat2=exp(a2-b2/(t+c2));
    p=0.1*x*psat1+(1-0.1*x)*psat2;
    while abs(p-90)>5
        t=t+1;
        psat1=exp(a1-b1/(t+c1));
        psat2=exp(a2-b2/(t+c2));
        p=0.1*x*psat1+(1-0.1*x)*psat2;
    end
    t(x+1)=t                            % <---- here t is an array
end

Try creating an array for your t values:

tArray = zeros(11,1);
for x=0:10
    t=70;
    psat1=exp(a1-b1/(t+c1));
    psat2=exp(a2-b2/(t+c2));
    p=0.1*x*psat1+(1-0.1*x)*psat2;
    while abs(p-90)>5
        t=t+1;
        psat1=exp(a1-b1/(t+c1));
        psat2=exp(a2-b2/(t+c2));
        p=0.1*x*psat1+(1-0.1*x)*psat2;
    end
    tArray(x+1)=t;
end

I'm assuming that you mean to reset t to 70 on each iteration of the loop. Is this correct?

MATLAB: Calling Upon previous anonymous function results for use in a second anonymous function

You can use one anonymous function (or any other function) is a second function. You simply have to call it as a function in the second function.

Try this:

Psat1 = ...;                                % Provide Value
Psat2 = ...;                                % Provide Value
P_x = @(x1) Psat2 + (Psat1 - Psat2)*x1;     % First Anonymous Function

y = @(x1) x1.*Psat1./P_x(x1);               % Second Anonymous Function

--------------------

EDIT —

This works for me:

Psat1 = rand;
Psat2 = rand;
P_x = @(x1) Psat2 + (Psat1 - Psat2).*x1;                            % First Anonymous Function
y1 = @(x1) x1.*Psat1./P_x(x1);                                      % Second Anonymous Function
P_y = @(x1) Psat2 + (Psat1 - Psat2).*((y1(x1).*P_x(x1))./Psat1);    % Third Anonymous Function
fplot(P_y,[0,1])

It is necessary to use Vectorization (link) in your functions when you combine them, so you do element-wise operations. (This will avoid warnings such as: ‘Function behaves unexpectedly on array inputs.’.)

Best Answer

Related Solutions

MATLAB: How to put the results from a while loop in a matrix

MATLAB: Calling Upon previous anonymous function results for use in a second anonymous function

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