need to plot this question

plot the compressibility chart using peng and robinson equation of state the values of Tr 1.0-1.5 (increment of 0.1) and Pr from 0-10 .. using the global for Pr and Tr

    pc = 220.55
    Tc = 647.1

[Chad Greene]

Please show that you've made some effort on your own. Upload the code you've come up with so far. If a specific step is holding you up, describe the problem in detail.

[James Tursa]

Please post what you have done so far and ask specific questions about it.

http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

[Nai Mansoor]

function [ y ] = PENG&ROBENSIO( z )
%UNTITLED Summary of this function goes here
%   Detailed explanation goes here

global Pr
global Tr
Pc = 220.55; %bar
Tc = 647.1; % k
w = 0.345;
alpha = (1+(0.37464+1.54226*w-0.26992*w^2)*(1-sqrt(Tr)))^2;
yy = 0.45724;
omega = 0.0778;
q = yy*alpha/(omega*Tr);
b = omega*Pr/Tr;
e = 1-sqrt(2);
o = 1+sqrt(2);

y =(1+b-(q*b*(z-b)/((z+e*b)*(z+o*b))))-z;

end

Answer 1

[Michael Haderlein]

Please... Did you ever write this into the Matlab editor? If so, you would see that the error is in the very first line - you cannot have a & character in the function name.

Some more errors will appear running the program as Tr seems to be an array. You need element-wise operations here. Until you know you want matrix operations, you can simply replace all * by .*, all / by ./ and all ^ by .^ (the dots indicate element-wise operations).

What really surprises me is the fact that the use of the globals Pr and Tr seems to be part of the task. Is that really what your teacher wants you to do?

[Nai Mansoor]

yes i correct the error of the first line but the problem in the script file if i used fzero it always says that there is an error yes thats the teacher wants me to do am to confuse about it

[Michael Haderlein]

Did you have a look on James' link? Right at the beginning it says:

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3) Show what you have attempted so far and if you have got:

• an error then post the whole error message. We need ALL the red text, not just a small part snipped out of it. This means line numbers, actual lines of code that generated the error, traceback to prior functions, etc. - everything that is in red color.

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