Problem with Runge-Kutta script file

[hagopbul]

TL;DR

trying to run a multiple dependent script files at the same time but it is not working on matlab

Hello :

trying to run mutiple script files on matlab (matlab basic online) but it is giving an error message the files are about runge - kutta method and applying them on a ODEs

the 1 script file Lornz :
function dy = Lornz(t,y,sigma,beta,rho)
% y is the 3 dimensional state vector

% y(1) =x , y(2) = y , y(3) = z
dy = [
sigma*(y(2)-y(1));
y(1)*(rho-y(3))-y(2);
y(1)*y(2) - beta*y(3);
];
the second file rk4singlestep
% rang kuta function to solve the lorenz example or other function

function yout = rk4singlestep(fun,dt,tk,yk)
% fun is a function i should load into the memory from file or command
f1 = fun(tk,yk);
f2 = fun(tk+dt/2,yk+(dt/2)*f1);
f3 = fun(tk+dt/2, yk+(dt/2)*f2);
f4 = fun(tk+dt, yk + (dt)*f3);

yout = yk + (dt/6)*(f1+2*f2+2*f3+f4);

the 3ed sript file :
clear all ,close all , clc


% inputing the lorenz example parameters

sigma = 10;
beta = 8/3;
rho = 28;

% the initial condition of the lorenz function
y0 = [-8;8;27];

% computeing the trajectory
dt = 0.01;
tspan = 0:dt:4;
Y(:,1) = y0;
yk = y0;
for i=1:length(tspan)
time = i*dt;
ykplus1 = rk4singlestep(@(t,y)lornz(t,y,sigma,beta,rho),dt,time,yk);
Y = [Y ykplus1];
yk = ykplus1;
end
plot3(Y(1,:),Y(2,:),Y(3,:),'b')

the idea is that the 3ed script file load or call the function in the 1st and 2nd files

the error message
Unrecognized function or variable 'lornz'.Error in simulatelorenz>@(t,y)lornz(t,y,sigma,beta,rho) (line 20)
ykplus1 = rk4singlestep(@(t,y)lornz(t,y,sigma,beta,rho),dt,time,yk); ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error in rk4singlestep (line 5)
f1 = fun(tk,yk);^^^^^^^^^^^^^^^^
Error in simulatelorenz (line 20)
ykplus1 = rk4singlestep(@(t,y)lornz(t,y,sigma,beta,rho),dt,time,yk); ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

the idea of this code to load the functions from other files but it is not working at all , tried to change few lines it didnt work out i cant figure out what is wrong with this code

Best Regards
H

 

[BvU]

Hi,

Could it be as simple as using Lornz instead of lornz ?

( and putting t = 0 ; before the call to rk4singlestep )

[edit] Disclaimer: I don't have MatLab, used Octave instead.

Put all in one .m file :
(then t=0; wasn't even necessary)

$\$

 

[hagopbul]

ahaaaaaaaaaaaaaa
days and i am looking at it say why it is not working !!!!!

i downloaded octave but using old windows so it is saying entry point not found

 

[BvU]

I don't know what to say. Not an expert: all trial and error experience

I have W10, double-click RK_ODE.m and do

>> RK_ODE

at the command prompt; that does the trick for me.

Do you have any .m file that runs at all ?

Can you post the complete error situation ?

[edit]If I first start up the Octave environment from the taskbar, I get

>> RK_ODE
error: 'RK_ODE' undefined near line 1, column 1
>>

then bring RK_ODE.m to the editor, click Run (green arrow, F5) and add the path, it also works fine.


$\$

 

[hagopbul]

it worked on matlab online ( basic) ( matlab basic is the free edition of matlab) but for octave i downloaded it and didnt work (the octave didnt run)