how i solve Approciman​tCoefficie​ntsSIR in MATLAB

I want to solve the approximantcoefficientsSIR,but it keep showing the error in line4

alpha=2.73; r=0.0178; I0=7; S0=254; %input parameters 
t=0:0.01:6; %time interval 0 to 6 in increments of 0.01
N=25; %number of terms in the approximant, increase until answer stops changing
[A,Sinf,a0,a]=ApproximantCoefficientsSIR(N,alpha,r,S0,I0);

Unrecognized function or variable 'ApproximantCoefficientsSIR'.

kappa=r*Sinf-alpha;
Ssum=1;
for j=1:N
Ssum=Ssum+A(j)*exp(kappa*t*j); %approximant (equation 4.7a in paper)
end
S=Sinf./Ssum;
plot(t,S,'displayname','S'); hold on
I=alpha/r*log(S/S0)+S0-S+I0;
plot(t,I,'displayname','I');
R=S0+I0-S-I; %b/c S+I+R=constant
plot(t,R,'displayname','R'); xlabel('t'); legend show

Answer 1

[TARUN]

Hi @MOHAN D,

Make sure that ApproximantCoefficientsSIR for approximating the coefficients of the SIR model, is properly installed in MATLAB.

You can run “which ApproximantCoefficientsSIR” command in MATLAB to check if the function is recognized and correctly installed.

Alternatively, you can use ode45 to solve the SIR model.

Feel free to go through this answer to get an idea on how to use ode45to solve SIR model:

https://www.mathworks.com/matlabcentral/answers/709538-ode45-solver-sir-model

Learn more about ode45 here:

https://www.mathworks.com/help/matlab/ref/ode45.html

Answer 2

[Walter Roberson]

approximantcoefficientsSIR requires the installation of a File Exchange contribution https://www.mathworks.com/matlabcentral/fileexchange/75131-approximantcoefficientssir