How to make this into a Logistic Map while keeping most of my previous work?

function [v,err,count] = Clapeyrons(P)
% Calculate molar volume as predicted by the Ideal Gas Law equation
% using the Newton-Raphson algorithm with initial estimate
% determined by ideal gas law.

% Inputs:
R = 0.082057; % Ideal gas constant in L atm / K mol
T = 293; % Temperature in K
Tc = 416.90; % Critical temperature of Cl2 in K
Pc = 78.72918; % Critical Pressure of Cl2 in atm
% a and b are Van der Waals constants for gas considered in
% atm L2/mol2 and L/mol respectively.
a = ((R^2)*(Tc^(5/2)))/(9*Pc*(2^(1/3)-1));
b = (R*Tc*(2^(1/3)-1))/(3*Pc);
P = 1; % Pressure in atm

% Outputs:
% v equals molar volume in L/mol as predicted by 
% equation for gas considered at temperature T and pressure P.
% err equals modulus of function evaluated at approximate root.
% count is number of iterations taken by Newton-Raphson algorithm.

% Version 1: created 24/04/19. Author: Paul Curran
% Version 2: created 06/02/20. Author: Paul Curran

if (~isscalar(P)) || (~isreal(P)) || P <= 0
error('Input argument P must be positive real scalar.')
end

Iteration_limit = 20; % maximum number of iterations permitted
Tolerance=10^-7; % maximum acceptable value for modulus of

A = (a*P)/((R^2)*(T^(5/2)));
B = (b*P)/(R*T);
v = R * T / P; 
Z = (P*v)/(R*T);

% Employ ideal gas law to obtain initial estimate
for count = 1:Iteration_limit + 1
% Terminate with error message if iteration limit exceeded:
    if count == Iteration_limit + 1
    error('Iteration limit reached. Iteration did not converge.') 
    end
f = (Z^3) - (Z^2) + (A-B-(B^2))*Z - (A*B);

% Terminate iteration if function is sufficiently small at current
% estimate
    if abs(f)<Tolerance
        break
    end
    f_dash = 3*Z^2 - 2*Z + (A - B - (B^2));   % Evaluate derivative of f
    Z = Z - (f/f_dash);   % Newton-Raphson iteration
    v = Z*R*T/P; % molar volume found using Newton-Raphson
end
err = abs(f); % Error is magnitude of f(v) at final root estimate
end

P = [1,1.5,2,2.5,3,5,10,15,25,50,100];
R = 0.082057;
T = 293;
Tc = 416.90;
Pc = 78.72918;

V_real =zeros(11,1);
V_ideal =zeros(11,1);
for count = 1:11
V_real(count) = Clapeyrons(P(count));
%[v_real,err,count]=
%V_real = arrayfun(@(x) Clapeyrons(R,T,a,b,x), P);
V_ideal(count) = (R*T)/P(count);
%V_difference = V_ideal - V_waals;
end
plot(P,V_real)
hold on
plot(P,V_ideal,'x')
title('Molar Volume vs Pressure for Cl_2')
xlabel('Pressure P (atm)')
ylabel('Molar Volume v (L/mol)')
legend({'Redlich-Kwong Equation','Ideal Gas Law'},'Location','northeast')

I need V_real to be a logistic map that goes through points P. How do I set that up?